RTN11,
I don't think it is even a case of getting low hour guys in cheap.
Where I currently work part time I was looking into getting my no applied instruments restriction lifted, but it would only get me an additional £2 per hour over the rate for teaching PPL, considering the cost of renewing my SPA IR ( I only keep an MPA IR current these days) and doing the 5 hr course it was questionable if it was worth it.
For the small modular schools teaching CPL on the side of ppl training then yes I would be very surprised if any one was getting more than £35 per hour for the singe engine CPL training.