I too have been let down badly by flight schools in the US. I'd be the first to say avoid JAA pilotmills at all costs.
My point is it is possible to find schools accross the US where the rate is significantly cheaper than in the UK, and, especially when it comes to hour building with no VISA's you aren't restricted to one school. If you have trouble getting an airplane at one, move on to another.
I don't know how much you charge, (and I'm sure your airplanes are nicer!) but for a large block of hours, I can't imagine the UK being cheaper.