Of course one should be endorsed with a ME type rating prior to commencing a SE IR(H) to ME IR(H) extension...I thought that was not an issue here.
SPH MET (H) TR - 8 hours in helicoper excluding skill test (a part of it may be done in a FS/FTD though).
As for the SE IR(A)-SE IR(H)-ME IR(H) route, please find attached the following:
JAR–FCL 2.205 Flight instruction
(See Appendix 1 to JAR–FCL 2.205)
An applicant for an IR(H) shall have
participated in a course of integrated flying
training which includes training for the IR(H)
(see JAR–FCL 2.165) or shall have completed
an approved modular flying training course as
set out in Appendix 1 to JAR–FCL 2.205. If the
applicant is the holder of an IR(A) the total
amount of flight instruction required by Appendix
1 to JAR–FCL 2.205 may be reduced to 10
hours.
JAR-FCL 2.240(a)
(4) The holder of an IR(H) valid for a
single-engine helicopter type wishing to extend
for the first time the IR(H) to a multi-engine
helicopter type shall satisfactorily complete a
course comprising at least 5 hours dual
instrument instruction time of which three hours
may be in FS or FTD 2/3 or FNPT II/III, plus a
multi engine skill test in accordance with
Section 5 of Appendix 2 or 3 to JAR-FCL 2.240
on that type, at an approved FTO/TRTO.]
All the best