I've never been to Cabair Wycombe or Denham but I almost did the CPL/IR with Cabair Bournemouth, however I chose not to as the Instructor-Student ratio was very high and the guys doing it spent a lot of time sitting around waiting for an instructor.
I've also heard rather negative comments about them, although their 'london' schools may have a completely different set-up to Bournemouth. My advice would be to go down there yourself and have a good nose around.