just have 15 hours to go to have the minimum to start the ATPL's.
If by ATPLs, you mean the ground theory exams, then there is no minimum hours requirement in order to enrol on a groundschool course. You must hold an ICAO PPL (H) for ATPL(H) and PPL (A) for ATPL(A). The 155 hours requirement is in order to start the CPL flying course and most courses will not let you start the CPL training until you have passsed all the exams.
Is this the interim course of H specific I wonder?
It is the interim system. Personally, I'd look at CAPT which is helicopter-specific.
Cheers
Whirls