If you are anxious not to spend too much to begin with, you can pick up pretty good suits
on ebay, especially at this time of year; if you can get something for a good price and you aren't a "difficult" shape-size, you could use it for a year or two and then get something MTM. Quite often, suits with worn/damaged/perished seals will be fairly cheap on ebay, yet getting them replaced in the UK is a doddle and cheap. I was quoted 18quid by Protec for a new neckseal replacement, incl labour, which was less than the materials would cost me here.
Having said that, the prices of new drysuits in the UK are very competitive, I live in Aus but it's still way cheaper to get one over in Blighty.
Protec suits are very competitve, you can get a base model, MTM for around 300 quid (I think). You'll need an undersuit but you can pick those up at a very reasonable price on fleabay too. I've been using the bog standard model for 5 years now and apart from replacing the neckseal, it hasn't needed any work (apart from on the colour but that particular wound was self-inflicted).
My next suit will probably be a Seaskin though.