Some years ago when the CAA would assess your experience against requirements I asked this question. I sent in my logbooks and experience (RAF Nav and A2 QGI) and was told I needed to demonstrate Commercial theoretical knowledge (CPL/ATPL exams) and complete sufficient training to cover all items of the syllabus to include IF and Nav, not less then 5hrs. I think an exemption similar to this would still be very appropriate if only it could be accepted.