I couldn't agree more with the others. Unless you're really keen, and would love to DIY, I would go for a local kitchen fitter.
Today's kitchens are quite specialised. I've fitted plenty over the years. I can do it well, but the guys who do nothing else can outpace me any time.
It's likely that the local fitters would be the same ones that B&Q etc would send anyway. Unless you're having units made, it's a fitter you need, not a joiner.
Certainly shop around for appliances too. It makes no difference to the fitter.
Howdens are good. They know the local tradesmen as well. They won't recommend anyone who isn't up to the job.
B&Q are fine these days... just expect for some of it to be missing, or out of stock ;o(