GTS seem to do a distance learning CPL course:
http://www.gtserv.co.uk/cpl_course.htm
I did my ATPLs with Bristol who I found to be very good. I guess you could also ask them if they would do their ATPL course for you at a discount, as you only need 9 subjects. It would make your refresher sessions before the exam quite relaxing if you could skip some of the classroom sessions.
Good luck with your training ! If I can't get a non-instructing job after a year or 2, then I think the route you're following would appeal to me a lot as well. Love the idea of instructing, and love vintage planes. I think I'd have to find another source of income as well though !