Looking at the spec of the high end iMac and the UK price of £1799 the sum of the parts don't really excite me. For starters, same processor as a year ago and a mid range gfx card - these specs, for the money, were looking a bit long in the tooth a few months ago (that's being generous) but are going to look even worse as the months go on.
I don't expect some major re-design in the next update but do expect and more exciting internal overhaul next time round - this revision just seems a bit lazy (chuck a bigger HD in, a bit more RAM). I think that the fact it's a fairly low key revision says a lot and reckon come November we may be more impressed with what Apple have to offer (pure speculation on my part).
As for the UK price, of course the pound is weak but the iMac price structure really does stick out like a sore thumb over here compared to the competition, they cross a psychological barrier for many would be purchasers. Personally I would stretch to the cost of the high end IF I felt that I was buying a computer with up-to-date parts but alas, not this time, Apple need to do better to convince me that their premium price is worth it.