You don’t always get what you pay for in life, but the wetsuit market is very competitive and price is generally a good guide to performance. If you’re thinking about surfing in winter in most of Europe forget anything that claims to be a winter suit below about £150.
Between £150 and £300 your suit just gets warmer and warmer and also more flexible and more comfortable to wear (in fact they’re directly related, the more stretch in the neoprene the better the fit = more performance and more warmth).
Above £300 you start to move into luxury territory. The little features that make the coldest days a pleasure. We can all survive without them, but if you’re committed and spend a lot of time in the water an extra £100 takes you to the absolute cutting edge of winter wetsuit technology.