We have just decided to use Benchmarx.
Wickes were good but DH can get the trade discount, and the units are the same- just come pre assembled rather than flat packed. It was cheaper to do that and get our own builder as the Wickes builders quote was high too (and we needed extra stuff doing than just removing and refitting the units).
We were told by a few companies that the carcasses are all the same so go for the finish you like, as the overall cost difference is not great between their cheapest and most expensive (unless getting solid oak of course)
Wren were competitive but unresponsive to standard questions, would not give a detailed breakdown of costs and the reviews and speaking to builders is, if anything is missing or damaged they take ages to sort it.
Howdens were more expensive than Wickes, and the finish on the units not so nice.
Ikea are good but they didn’t have the finish we wanted.
We are getting the quartz worktop separately and saving c2k on the Wickes quoted price. Our existing laminate top has lasted 30 years though with only 1 burn mark!
We have bulk bought all our appliances from an online company who hold them until needed for a credit card deposit (so protected) and will price match if the prices drop in the meantime. Def shop around for these.
Tiles also being supplied by an online company.
Breaking the component parts down has saved us thousands! Whoever you go with, get a detailed breakdown and see if any of it can be sourced separately.