As Big Finish squeeze more and more tales into the main range, following the order (if you care!) becomes more and more complex. Sometimes there are insufficient clues, or you need knowledge I don’t have. Other times it is more straightforward.
My vision is to come up with a picture that links all the tales together – probably a dream, but I will give it a go!
PS – I have now (eventually!) found the wiki that covers all of this (update October 2012: since deleted) so all I need to do now is navigate all that, lose the non-Big Finish material and there I have it!