The UK is not such a small part of Europe economically. It just accepts European regs without question and with enthusiastic enforcement, whereas the French and the Italians sign the treaties, pick the bits they like and informally ignore the rest.
The UK does have the biggest GA scene in Europe, and (judging from how much activity one sees flying around Europe) by probably a big margin.
There is some GA in Germany, a bit in France, and the rest of Europe is more or less dead - except for ultralight "pure sports" activity operating close to the ground. That is probably the real reason why the UK gets sidelined in Europe on GA issues. Most of the national reps on the committees (being ex air force or ex national airline ATP types) have not seen any domestic GA pressure.