That's not the case. The difference in driving laws (right vs left lane) makes it fairly difficult to move cars between GB and mainland Europe, because cars have to be physically modified.
Insurance companies are just out to make as much money as possible; in Europe their life is hard because they don't enjoy the ridiculous margins from crazy markets like US healthcare, they have to obey stricter regulation, and suffer from heavy rates of fraud in many countries.
Yes, but this is not comparable to cars being "spirited off" across the continent, which don't need to be split up or modified: I can move a car from Prague to Paris and get full whack for it. This is not the case for the UK market, which enjoys a little bit of a barrier compared to the rest of the EU. Proof of this is that the secondhand market is still very much alive, because car prices are higher than elsewhere, since there is less pressure to align to cross-European prices. That is not the case in, say, France or Italy.