Sky Guy,
Funny enough, I decided to cross over to the JAR system as early as possible based on UK qualifications as it seemed the most cost effective. I now have frozen CAA ATPL exams locked into a JAR CPL(A)(R).
You are correct, its best to get confirmation in writing, so the CAA have written to me and confirmed that the minimum requirement for me now is to pass an IR and that can be done on a single. No further JAR ATPL exams required.
So I'm not getting succered into throwing more money on the fire. I still don't think there's any point in chasing a dead qualification. But if you want an ATPL based on flying around in C150's I'm sure the airlines will respect you for it !!!
Perhaps someone can verify your claim - I have it writing from the CAA and I'm very happy with the letter - thanks....