LAFalot
I don't think HeliAir at Denham offer training on the H500.
Elpirata
This forum is very useful for exchanging experiences of all sorts, including good/bad places to train/rent. Perhaps the reason lots of people recommend HeliAir is that they have good quality machines (and lots of them), give good service/training and, apart from the CFI who always looks as if she could do with something to put a smile on her face, very easy going and friendly.
Bad experiences/reports are just as helpful. eg The small place opposite Leeds Bradford used to be good but, since the change of ownership a few years ago, has consistently bad reports.
Knowledge is power - and can save lots of disappointment and dosh!