I sometimes fit kitchens in my job as a building contractor, I dont specialise in it though, I have experience with a few of the afforementioned companies but can only say as I have found. Wren seemed fine,quality good and easy to deal with(some parts were branded Howdens on reverse too).Howdens are a good company too, I used them sometimes and kept an account going for when a kitchen job came up, although Ive let it go now as I am starting to wind down. My experience with Ikea not so good,some end/fascia panels a bit flimsy (reversible)and had to use my own wall cabinet fixings as I didnt trust theirs,also they couldnt cut a worktop to the right length for us.After the third attempt( a week each time)we ordered it oversized and had it cut ourselves. One you might consider is B and Q higher end stuff,Cooke and Lewis, good quality,easy to get bits for and a good price(we got one ourselves).Of course you can pay as much as you like(and there are some cracking kitchens out there), but no matter how long it lasts, you might want a change of style after a few years anyway. As regards fitting, try to get someone whos been recommended or has fitted for friends etc as the fitting is probably the most important aspect. Anyway,good luck and I hope it goes well.