The King Air(and in partiular G reg) is certified single crew or multicrew, depending on the operation involved. If its flying multicrew then chances are its operating under an AOC with the relevant details in the Ops manuals as agreed by the operator and the UK CAA. Any flying time accrued in such an operating capacity counts towards the 500 hours multicrew requirement for the ATPL. The aircraft however is not a JAR 25 a/c therefore cannot be used for an ATPL skills test and as such you cannot 'unfreeze' an ATPL with it, irrespective of whether you are officialy operating it single or multicrew.
The aircraft can also be flown multicrew(as per AOC and Ops) by a PIC who does not hold an ATPL. A frozen ATPL will suffice. My local air ambulance being the classic example.
Once EASA gets it claws in everything however, all my change!!
