SimJock,
Yes WC, a very convincing demonstration of what can be done, believe him everyone else it can be done. I shall be testing this new found knowledge on Gatwick next time I'm airborne , last time I tried with them they didn't even reply to me after several calls, so maybe this time will be different.
As an 'umble occasional Gatwick approach controller we don't train folk to ignore r/t calls.
If they didn't reply the chances are they did not hear you or you were trying on the wrong frequency
Always feel free to request transit, but please just a little forethought in what you ask for.
WF.