reddo
I have been out of the UK scene for a while now but I think that you would have to do the Helicopter bit of all the ground exams
(theory of flight, basic gas turbines if you haven't alraedy done it on planks). I also reckon that you will have to do 30-40 hours helicopter including all the GFTs. You will probably have to do Navs as well!
As I say, I am not really in the UK scene now and my info may well be out of date. Try calling the CAA and speaking to Mike
Fooks-Bale who heads up helicopter training. He is a ex Bristow man and is extremely practical and knows his stuff (not just the books either)