have you looked at the IKEA kitchen design tool? it's quite fun to play around with, and you can try all sorts of permutations to get the kitchen you want. You basically try all the units for size, then add the doors/handles you like afterwards, so you can fit everything in before doing the final 'covers' as it were.
We got our kitchen from IKEA, and despite being, um, not very computer literate, I designed the whole thing and we got it for just over £3K, then we got an independent cowboy builder to fit it for us - to be fair, the fitting was fine, the finishing touches were quite shambolic though, and he kept disappearing for afternoons then reappearing at 6 with power tools and disappearing again for a day or so. However, think we got him to do fitting, electrics, plumbing, plaster for £1.5K (he had pet electricians and plasterers to do those bits).
Also worth going to places like Homebase and B+Q to get them to design you a kitchen based on your measurements, just to get an idea of what's possible.
We liked the IKEA payment plan (0% credit for 1 year if over £1500, 2 years if over £3000), so went with them (plus loved their kitchens) - others I know have used Homebase and loved them.
have fun though :o