Totally depends on your budget and your expectations.
Are you:
A) looking to buy the units, appliances, worktops & tiles yourself and employ trades to complete the kitchen yourself (carpenter/kitten fitter, tiler, flooring, electrics etc)
Or are you
B) looking for a kitchen company that will help you design and then supply and fit your kitchen from start to finish.
I've done option A for a small kitchen in our annexe earlier this year. units from DIY Kitchens, worktops from Howdens, oven, hob, fridge all sourced from the Internet and trades we know to fit etc. It's a nice finish, but took time to achieve given the availability of the different trades we needed.
For our main kitchen and scullery we are going for option B. Yes, it's more expensive but we want a high quality look and feel so have gone for a handleless kitchen from a German brand with lots of extras like touch open/close cupboard doors plus we are able to have the custom sized units so we can accommodate some odd spaces we have without compromise. It's up to the kitchen company to mange the whole job, from removing the old kitchen, replacing the ceiling, rewiring the kitchen and then installing the new units, appliances, worktops and splashbacks etc. We've gone with a local independent kitchen company with an excellent reputation and winner of national awards for kitchen design. Some of the ideas they brought to the table have made a huge difference to final design and are things we would never have thought of. Their eye for detail is incredible l.