Have you looked in LASORS? See
http://www.caa.co.uk/srg/licensing/f...sp?groupid=292 for the on-line version (in .pdf format).
Regrettably, as you don't meet the full accreditation hours totals, you won't receive much ATPL(H) theoretical knowledge credit.
To quote LASORS Section G4:
"There is no direct route to a JAR-FCL ATPL (H) for a QSP (H). In order to qualify for a JAR-FCL ATPL (H), applicants must qualify for an IR (H) and a type rating for a civil helicopter type certificated for a minimum of two pilots under IFR, or a helicopter type required to be operated by two pilots under JAR-OPS."
"For this reason, a QSP (H) will not qualify for a JAR-FCL ATPL (H) unless he completes an IR (H) in accordance with Section E, and an approved type rating course for an appropriate civil helicopter type, in accordance with Section F."
"Full details of the JAR-FCL ATPL (H) requirements, including credits available, are detailed in Section G3."
"A QSP (H) should refer to Section D6 for details of the requirements to obtain a JAR-FCL CPL (H)."
Wouldn't it be simpler, cheaper and quicker to go for a CPL(H) first?
Good luck, whatever you decide to do.