Self study is a good route to go. You can take it in your own time and then attend a brush up at the end to help with anything you're stuck on!
I am doing the Bristol Groundschool- their pass rate is fantastic and the brushups really get you ready for the exams.
Depends on other commitments. I work full time so full groundschool was not really an option, but I don't think you need it anyway.
It won't necessarily take longer to do distance learning if you have the discipline to study. I know I guy who did the first 8 in 2 months and passed them all no problem.
Good luck whichever way you go!