Good afternoon
I instruct/examine at The Pilot Centre, Denham and you are right in that we do not do CPL/IR training, for now. Its been about seven years since I did my commercial and the same posts appear now as they did back then! Everyone knows someone, who knows someone who had a bad experience with their training school.
I am not sure if Cabair at Denham and Elstree do CPL/IR training, I dont think so? At Wycombe they do, formerly Wycombe Air Centre, who I did my Multi-engine rating with and were good back then but have had no dealings with them of late.
In my opinion, for what it is worth, you have to go on your (informed) instincts, go to the schools and form your own opinion. Things I looked at were condition of facilities/aircraft, amount of aircraft and students (ie if only one aircraft and it was tech, what are they going to do?) and obviously cost, but importantly extra's, positioning for test etc.
I did my CPL at Naples Air Center, Florida, at the time could not fault them. The IR was at Aeros, Gloucestershire, where I commuted most days! 2 to 1 instruction, good sim/aircraft, airspace was a little less busy! Exam centre close by and the price was the cheapest and exactly as quoted!
As I say take a couple of days out and drive about.
In the meantime a well taught IMC rating will help build hours (if needed) and will be a good step towards the IR. (And yes of course we could help with that!!)
Good luck
Feel free to ask further questions