@Milo; The good news is that I spoke with the head of training of Agusta last week and they are after all willing to take my ATPL skills test. They do say this is considered an exception and I need to present a letter from my authority requesting such a test to be conducted by Agusta. So after all my problems should be solved by the end of next month.
@QTG; Now this is where things get interesting. I used the exact same arguments that you presented while communicating with the Dutch CAA and they did still did not accept it. So I entered into contact with the UK CAA to get their "ATPL skills test on the 135" policy/view in writing to present back to the Dutch authorities. The answer below is the official UK CAA response and leaves me slightly confused as to what they are actually saying. Especially since I know for a fact, just like you said, they have been issuing ATPL licenses based on a skills test done on the 135...
[Q. Does the UK CAA acknowledges that Bond's EC135 with the Dual Pilot IFR kit installed are regarded as certified multi pilot helicopters and are therefore accepted for the conduct of an ATPL(H) skills test.]
Regarding the conduct of an ATPL(H) skill test on a single pilot certified helicopter in the UK, I have the following comments to make:
Answer: Unfortunately not, however I should clarify that this is not specifically a certification issue. The English language version of Commission Regulation (EU) No 1178/2011 (as amended) in Annex I (Part-FCL) at point FCL.010 defines a multi pilot helicopter as ‘ [the] type of aircraft which is required to be operated with a co-pilot as specified in the flight manual or by the air operator certificate or equivalent document’. Thus a helicopter which is certified for operation with only one pilot may nevertheless be a multi pilot helicopter for pilot licensing purposes if it is required to be operated with a co-pilot by the air operator certificate or equivalent document. Part-FCL in Subpart H then sets out the requirements to be met to qualify for a multi pilot helicopter type rating. To qualify for an ATPL(H), an applicant must, amongst other requirements, pass an ATPL(H) skill test in a multi pilot helicopter (see point FCL.520.H). This presupposes that the applicant has qualified for a type rating for the multi pilot helicopter to be used on the test.
A pilot does not need to be employed by the AOC but as noted above, must complete (or hold) a multi pilot type rating for the helicopter used for the ATPL(H) skill test. The MPH type rating course must be approved and incorporate [ … ] AOC MP SOPs, which Bond do not currently have. The only UK operators that do hold this approval at present, formally, are a small selection of the UK North Sea off-shore operators.
In clarification, the ATO must also be an AOC holder with approved MP operations in the SP certified helicopters for which MPH type ratings are sought. It should be noted that once a pilot has qualified on a type, they can take the rating with them to any operator (whether qualified as a single or as a multi pilot helicopter). AOC SOPs will then be addressed through the Part-OPS operator conversion courses, etc..
While this may not have been the response you were seeking, we hope it provides you with some further clarity as to the current requirements.