Try Astraeus at London Gatwick. Three pilots they have trained have now started with EZY on the 737 with more to come, I'm sure.
They have an assessment procedure to check that you're good enough and the training you get is just the same as the airline training, so it's pretty good.
The cost is about UKL 16,500 including base training and their website is at:
www.flyastraeus.com
Good luck!