As another PPL who has not "dared" ask for an SVFR across London, this is a very enlightening post. Having flown the LAX "Special Flight Rules Corridor" and the PHX transition routes many times (yes, even recently), I remain surprised by how opposed UK ATC are to accommodating similar arrangements. After all, PHX is pretty busy and LAX is jolly busy...
ATCO 2's response is very much more helpful.
I am not aware of anybody at my club (located at Elstree) who has knowledge or expereince of crossing London under SVFR. It was certainly not a part of my training (which always headed firmly north-west).
A look at the LAX terminal chart will show that the various zones there are at least as complex as those around London, then factor in Santa Monica, Long Beach, Orange County, Hawthorne, etc.
The controllers there appear able to cope, indeed they do not want to speak to you in the LAX corridor, you simply squawk 1201 instead of 1200 and free-call on a dedicated freq. At both LAX and PHX, the route is directly overhead the active runway numbers and I am sure there are similar arrangements at other busy US airfields.
Why is it that our ATC is so much more negative?
Mind you, I reckon I would rather make this request to Heathrow than to Essex Radar.....