Oneflewover,
I did the conversion a few years ago, just as the CAA were offering it. To say it was fairly simple would be over complicating it!
Not too sure about what the hours requirements were but your best bet is to talk to Alex Whittingham at Bristol Ground School. He seems to be the 'guru' on the conversion and he helped with mine.
Off the top of my head I seem to remember doing PofF fixed wing, Performance, Operational Procedures and a 100 question bridging exam made up of all the other relevant (or irrelevant) fixed wing bits of the other exams. There might be 1 more but I can't remember it as I dumped all of the useless rubbish after sitting them!
You will then need to do the CPL skills test and a Multi/IR which the CAA allowed me to do combined in 10 hours before the CPL thus reducing the CPL training to 15 hours. You can then blunder off to somewhere cheaper to build the hours for the license issue if you don't have them.
Not wishing to get spanked for advertising but you might want to chat to Brian Marinden in Exeter as he specialises in 'advising' rotary to fixed wing chaps from the forces.
Good luck!