I used Howdens and they are fine (and cheap). they have one in Wood Green. if you want to go for a higher end one, then I don't know...
Have a chat to Ross Day, he just finished installing a friend's kitchen on the ladder.
Local chap 07706927771
We had ours designed and fitted by Murdoch Troon (their protfolio here at https://www.murdochtroon.co.uk). Prices maybe slightly higher than in Howdens but their kitchen cabinets are made from real wood, and not mdf. The worktop is marble and the kitchen Murdoch Troon designed just fitted perfectly into our overall house interior which was a challenge in itself.