Yep, I bridged from ATPL(H) to (A) and it was the biggest pain in the a**e to get sorted for me. However its should all be sorted out with the CAA now.
Alex Whittingham at Bristol Ground school is a good point of contact as you will need a 'sponsor' to be able to sit the exams.
I can't remember off the top of my head the exact exams but I think they are:
PofF fixed wing, Operations, and Performance.
Then you need to do the 100 question 'bridging' exam. This was a bit of a mish mash for me but should have been finalised by now. Basically it covers all of the other 'fixed wing' parts of the exam syllabus that the CAA thinks isn't covered by the ATPL(H).
That's yer lot!
Good luck
