If this helps, I've just signed up with Riverside. I've spent months investigating the different options and found that financially Riverside is alot cheaper due to the US rates of flying. I've spoken to associates who are commercial pilots and they all said by doing the course in the USA the timescale is halved because the weather.
The other reason why I chose Riverside was the fact that they are a UK based organisation that does the flight experience in a place that is easlier on the purse.
I've also checked the threads on here by searching for riverside and there are good feedback.
The guy who runs Riverside is extremely nice and I've spoken to him for advice in the past whilst I was contemplating doing the CPL a few years ago and did not realise it was the same guy until I meet him at the Professional Pilot Show at Heathrow this year.
If this helps and you would like more information or my views PM me and I'll try and give you as much help as I can.