Hi Spike,
I think you are missing some crucial information.
The Bristol Groundschool course is also provided by means of course books / folders that you work through. These books are backed up by a CD-Rom that contains animations, text and I also believe progress tests that are marked instantly (I may be wrong there though).
Oxford Aviation provides their course in books as you say but I don't think they have a CD-Rom as part of the course.
However Oxford also author and distribute a few good titles for ATPL studies including, "Aviation Meteorology", "VFR Comms", "IFR Comms", "ATPL Question Bank", etc etc...
Usually one completes the ATPL studies in a year or so. However there is not really a time limit and it can take you longer if you so wish. However the CAA state that all of your exams must be passed within the 18 months after your first pass at ATPL level.
Hope this helps.
Best wishes,
Charlie Zulu.