He is sure because most of the pilots here have had their home licences converted to GCAA licences.
Most people come here with an ATPL, and some experience on the aircraft type they intend to fly, in those cases, the companies they work for know the requirements for conversion of a foreign based licence.
How about you email the GCAA directly? You will have to give them more detail than you've given us, and the answer you get will be from the horses mouth, as it were.