DFC
That was my point, subsequently backed up by Pub User, if you aren't working an ATC unit when crossing the International FIR Boundary, you squawk 2000.
If you are working an ATC unit, you squawk the allocated code.
I know that the UK London and Scottish Information will occassionaly allocate squawks to indicate to adjacent units that the aircraft is working them, but these are allocated codes specific to them, i.e. not 7000 or 2000.