Hi Mark, I've just started the Bristol course and from what I've seen, one of the best things about the software is it's course mode. You set up your start and finish dates and then it tells you what lessons you need to complete every day till you reach your finish date. You then have a graph to show you how far you've fallen behind or overtook the course.
I'm trying to complete module 1 in a 4 month period, so I've set the course mode up for 3 months, then I've 2 weeks revision at home followed by the revision course and exams in Bristol. With a bit of commitment I don't see it as impossible even with my full time job.
The course certainly seems to just get to the point but I'm definitely pick up a lot of stuff I didn't know.
Having said all that I've no idea how the Oxford CBT works, if the flight school use it, ask them if you can have a look at it and see if it would work for you.