Have just fitted cash and carry from Galway and found the service and product very satisfactory. And I am fairly fussy! So I would not dismiss them before having a look. I also know someone who got a B&Q kitchen and he too is happy. It depends on what youy want really - I know B&Q had lots of extras but to me those are the bits that will end up breaking or limiting use of an area!!
Anything that I feel a desperate need for that C&C didn't have I will buy elsewhere.
Whatever you buy make sure it is fitted by someone good. The only change I would make to C&C is I would ask them to put numbers on the cupboards and to match these to the plans!Its like a big jigsaw. We finished ours off with granite worktops and induction hob/electric cooker.
If it is a renovation have you considered retaining existing carcasses and getting new doors/worktops and appliances? It might also work out cheaper to get a good carenter to make a kichen to fit (older houses would have had differend sizes/layout and buying readymade might be tricky)