Interesting question, I’ll dig my teeth into it if you don’t mind! As a summary, yes, the Romans definitely saw the British natives as barbarians (but not as barbaric as the Germani, more like the ‘tameable Gauls’). But, an important point for understanding the Roman perspective - and their political and military decisions concerning the Isles - is to look at how Britain became the ‘ultimate trophy’ of Roman imperial project. Many emperors dabbled with the conquest of Britain, always wanting to get further than their predecessors. In the everyday life of the common people of Rome, Britain would have featured in the form of British traded goods, such as metals, dogs, timber and British slaves, and in the imperial propaganda where Britain was through art, coinage, etc. represented as subduing to Roman imperium - it’s difficult to say much more about the “general” view of the Romans, since the common people and provincials have left no written accounts about Britain for us. But, this is what the Roman literary sources tell us about Roman perspectives of Britain before and during the Roman conquest (of course, whole of Britain was never conquered but I’m using sources until the usual cut-point of Agricola’s campaigns and the more or less complete conquest of England).

So, what made the Romans to first set their eyes on Britain? Before Julius Caesar’s campaigns, the Romans knew practically nothing about Britain. The Isles had been in the trading sphere of the Graeco-Roman world for centuries already; Cornish tin was relatively common already before Caesar. The Greeks spoke of the enigmatic islands somewhere in North-West Europe, the Cassiterides (‘ Tin Islands’), which most likely at least partly refer to the British Isles. So, there certainly must have been some Greek and Roman traders sailing to Britain before Caesar and we do have some later reports of Greek and Carthaginian sailors that went there pre-Caesar. Nevertheless, in Rome, Britain was just something obscure in the shady edges of the Roman world. Plutarch actually says that some people did not believe that Britain existed even after Caesar came back, and thought his invasion campaign was completely made up (“The island [Britain] was of incredible magnitude, and furnished much matter of dispute to multitudes of writers, some of whom averred that its name and story had been fabricated, since it never had existed and did not then exist; and in his [Julius Caesar’s] attempt to occupy it he carried the Roman supremacy beyond the confines of the inhabited world” Life of Caesar 23.3).

So, the first tangible contact the Romans had with the British isles and the British came when Julius Caesar went on his campaigns to conquer Gaul (58-50 BC). Here’s the ‘best of’ of his insights of Brittons (from his monograph the Gallic Wars), i.e.stereotypical conceptions which probably had some truth in them but also a lot of misconceptions, which he carried back to Rome and which would shape Roman perceptions of Britons for centuries to come:

The number of the [British] people is countless, and their buildings exceedingly numerous, for the most part very like those of the Gauls: the number of cattle is great. They use either brass or iron rings, determined at a certain weight, as their money. Tin is produced in the midland regions… They do not regard it lawful to eat the hare, and the cock, and the goose; they, however, breed them for amusement and pleasure… The most civilized of all these nations are they who inhabit Kent, which is entirely a maritime district, nor do they differ much from the Gallic customs. Most of the inland inhabitants do not sow corn, but live on milk and flesh, and are clad with skins. All the Britains, indeed, dye themselves with wood, which occasions a bluish color, and thereby have a more terrible appearance in fight. They wear their hair long, and have every part of their body shaved except their head and upper lip. Ten and even twelve have wives common to them, and particularly brothers among brothers, and parents among their children; but if there be any issue by these wives, they are reputed to be the children of those by whom respectively each was first espoused when a virgin.
Julius Caesar, ch. 12-14

The fierceness of the British in battle comes clear from Caesar’s accounts of fighting with them. Caesar himself says that his reason for sailing to Britain was to subdue Britons that were helping the Gallic resistance, which might be partly true, but it might have been just an excuse to continue his project and conquer territories in Britain, too. His main motivation for the conquest was probably just to reap some good old immortal glory. [I personally think that the Roman imperialism is sometimes represented as overly cold and calculating, motivated by rational economic and political gains, carried out with effective and sophisticated tactics. But, the Romans were clearly obsessed with conquering just for the sake of conquering, and we should not underestimate how much of Roman imperialism was shaped by individual generals' and emperors' zeal to acquire military victories and spoils] As many scholars have argued, it was symbolically significant for the Romans that Britain was an island - separated from the continent, a physical form of independence - the subduing of which the Roman emperors were dying to get on their CV.

Julius Caesar’s invasion was seen thus as especially daring; he was the first Roman to cross the Atlantic with an army to an unknown island and an island that was believed to be massive, as Plutarch puts it. Most likely Julius Caesar had better intelligence of the Isles than Plutarch. Regardless, Caesar made two attempts to establish Roman power at the Isles, which failed partly because of bad weather and partly because, out of ignorance, he did not realise what an hubristic project subduing Britain was. But, although Julius Caesar’s military campaign in Britain was an epic failure (with substantial losses of men and ships), the Roman senate worshipped him for crossing to Britain and obtaining hostages, so, it played out well for Julius. Britain was seen so unattainable that the mere fact of being the first to get there was a remarkable achievement. But, Caesar managed to make a few alliances with British chieftains that gave Rome political influence in the Isles, and intensified the trade and cultural exchange, which helped to pave way to the eventual conquest of Britain.

Strabo, the Greek geographer, writing during the reign of Augustus, probably provides the best account of what sort of impression a regular person formed of Britain once the British slaves and soldiers and goods first started flowing to Rome:

Most of the island is flat and overgrown with forests, although many of its districts are hilly. It bears grain, cattle, gold, silver, and iron. These things, accordingly, are exported from the island, as also hides, and slaves, and dogs that are by nature suited to the purposes of the chase; the Celti, however, use both these and the native dogs for the purposes of war too. The men of Britain are taller than the Celti, and not so yellow-haired, although their bodies are of looser build. The following is an indication of their size: I myself, in Rome, saw mere lads towering as much as half a foot above the tallest people in the city, although they were bandy-legged and presented no fair lines anywhere else in their figure. Their habits are in part like those of the Celti, but in part more simple and barbaric — so much so that, on account of their inexperience, some of them, although well supplied with milk, make no cheese; and they have no experience in gardening or other agricultural pursuits. And they have powerful chieftains in their country. For the purposes of war they use chariots for the most part, just as some of the Celti do. The forests are their cities; for they fence in a spacious circular enclosure with trees which they have felled, and in that enclosure make huts for themselves and also pen up their cattle — not, however, with the purpose of staying a long time.
Strabo, Geographica IV.2