Vikings tried their best to stay near shorelines or islands when they could and would camp using wool tents. They only made the long journeys during the spring and summer as the weather was better for long distance voyages. It has been guessed that the sail could be brought down to act as a weather shield.

Once they landed they tended to stay in the UK for long periods of time.

Well, the short answer is that Vikings did not necessarily travel long distances in the type of ship shown.

I will preface this entire discussion by noting that the "longship" has been romanticized in the stereotypical Viking community all out of proportion to its actual use, and also that our archaeological evidence of actual longships is highly fragmentary. (The Gokstad and Oseberg ships which exist in the popular imagination as the "longship" are of the same type and buried within a few years and a few miles of each other, and may not be typical of anything other than their own mid-9th century style).

All that said, what we think of as the modal Viking warship of the 8th-11th centuries was the longship, which that appears to be a (very small) replica of. The longship was classified by its number of "rooms" (defined as an area between thwarts, or cross-members) with an undecked longship presumably having as many thwarts/rooms as pairs of oars, which we also assume corresponds to pairs of warriors. These are large assumptions, but the records we have from ship-musters in Alfred's England (for example) talk about ships in terms of rooms, without a lot of evidence for manning.

In any case, a ship of less than 20 rooms wasn't considered much of a warship at all, with ships of 20-25 rooms seeming to be average. King Harald Hardrada had a 35-room ship built in 1061-62, which was extremely large. (The ships of 20-25 rooms were called esnecca, "snakes," while ships larger than say 30 rooms were called drekkar or "dragons," and seem to have been celebrated in sagas as very unusual.)

In general, though, ships used for exploring voyages were not of the longship type. Longships were distinct from trading vessels by being, well, long in proportion to their width. We have some evidence that the Norse used fatter (for lack of a better term) ships that were mostly propelled by sails and had oars only at the bow and stern; the Bayeux Tapestry depicts English forces using some of these types of ships, with shields hung over the gunwale and oars at the ends of the ship. These trading ships are more likely to be ones that made longer voyages, with longships and other ship types following once the navigation was well understood. The trading ships the Norse used (knarrar) would have been partially decked over, as would larger longships have been, and would have offered some shelter from the elements.

It's important to keep in mind also that there was a specific season for voyaging, during the spring and summer and before fall rains and storms started. In northern latitudes, summer days are very long and give a ship's master plenty of time to navigate among familiar landmarks. By the time fall storms started, most voyagers would have hauled their ships up on a beach somewhere for the season and would have settled down to wait out the winter.

It would by no means have been a direct journey from Scandinavia to Britain. The vikings raided along the coast of Europe as far south as the Med, and the invasions of Britain were carried out by armies which had formerly been raiding on the Seine. They would have stopped off, and there is evidence of them having created trading bases such as Dublin. Also, the journey from Scandinavia to Britain would not have taken that long, and so shelter was likely not an issue.