I can only speak from my personal experience and Im sure there may be others out there who may say the exact opposite as me but...
I can only speak highly of Sheffield School of Aeronautics. I found that all the staff/tutors to be more than willing to help and the course was clear and concise (for me anyway). Its not simple. Don't expect to study 9-5 Monday to Friday. It won't happen. You have to put the work in before you arrive and evenings /weekends during your 5-6 weeks there. If you have the access and ability to complete the FAA ADX test before you arrive then that gives you some breathing space.
If you want further personal details of my experience (June/July 2010) then PM me and I'll supply what I can.
Either way, whoever you decide to study with. Best of Luck...