I used a local firm for mine, which is fantastic quality...no particle board etc and to be honest, I paid a buttload...but it was worth it. Its absolutely gorgeous (if I may say so myself) I would try some local firms also, they might be able to give you a good deal.
I have a BIG ASS kitchen, its 20 feet long...hence the expensive kitchen. But I bloody well love it!!! I had 7 quotes (hey I was on maternity leave, I had the time) and about 5 of them came in around £1k in each direction, and then I had 2 cheap ones (like 1/3 of the price) If I had to do it over again in a house I was going to sell, I would use the guy who built our kitchen and do an Ikea kitchen!!!
OOOH, Kutchenhaus in Manchester. They do FANTASTIC kitchens, I was going to go with them, but decided to go with a local firm. They do kitchens all over the country....I think their website is something like Germankitchens.com. Its worth a trip up here, their show room is fantastic!!!
eta...my friend used Wikes and their project management service and had a total nightmare!!! The project management service was based in Italy or something like that, they didn't turn up on the first day, the tiler that they contracted through Wickes dropped out etc etc. But on the other hand, obviously lots of people have had good experiences, so you have to take everything with a grain of salt.