If you don't do the IR within three years, and then later come to do it, you will have to sit 6 exams again. Similarly, if you have CPL(H) theoretical stuff!
Consider whether it would be easier for you to re-learn/revise something you studied three years hence or whether you would want to start studying again from scratch. The ATPL(H) GS is a more expensive route but given your hours and ambitions, it might be the more sensible one.
I've gone for CPL(H) GS but my circumstances are different!
Cheers
Whirls