Can't rate Bristol Ground School highly enough - although plenty of other courses get good reviews. I took 18 months, working full time and with a new baby(!) If you structure your week and dedicate yourself, you shouldn't have a problem. I even actually quite enjoyed the experience in a perverse way - it's something we all have to go through. There's also an online Bristol forum for help/advice etc.
The 2 week Brush-Up courses are intense and consolidate your months of study. Combined with the excellent question bank you'll be ready for the exams when they come. Good Luck ( Av 94%)