Pretty much. Coin usage starts around 100BC (assuming the Gallo-Belgic Staters were imported). However influence there was more Greek (the coin designs can be traced back to those of Philip II of Macedon) than Roman.

Wine was imported yes. Initially via Gaulish intermediaries (one of the things traded in return was hunting dogs). The fall of Gaul to Rome (and Caesar's invasion in the 50s BC) messed up the trade routes and seems to have resulted in political change in southern England.

Staffordshire? That's on the edge of the Corieltauvi territories. Less romanised than the southern kingdoms but they did strike coins.

The most readable source for coins of this period is Philip De Jersey's Celtic Coinage in Britain. For everything else Barry Cunliffe's Iron Age Communities in Britain: An Account of England, Scotland and Wales from the Seventh Century BC until the Roman Conquest