Thanks ruddman, as xxx said it's a replica of a Grumman Panther - apparently scratchbuilt and 75% scale, known as a Gross JG2. I was told that it has a modified helicopter turbine as powerplant, can't begin to get my head around what would be involved in doing that. Quite an impressive beastie and certainly something a bit different at the fly ins.
Only thing I'll say is I wish it were in a military colour scheme.
Edit: Apparently ripping the gearbox off a turboprop making it into a jet isn't unknown, most commonly to build jet drag boats.