2 sleepy,
I am currently doing my cpl @ stapleford however it is costing a fortune becauce of the weather. I was all good on my last nav about two weeks ago but now after about a week plus off Iam a bit rusty. Having said that if you do it in summer weather you can get it done in three weeks and pass first time. I personally know a couple of guys who did. There's a guy there who did his 170a a while back and he is still waiting to do his test. He's had to do 10hrs of revision just to keep current. You can check the cost yourself. My advice will be to start it in march where you are guaranteed about 70% good weather.
However you will recieve good quality training.