I have used SVFR several times to clip the NW & SW corners of the LHR zone. IMveryHO in terms of SEP land clear it is definitely feasible from 1000' anywhere except directly over Slough, which in any case is too easterly to be given approval. Again IMHO no other SVFR routes in a single through the LHR or LCY zones are legal. To be perfectly honest you don't need to be Pythagorus to realize that it doesn't save you a hell of a lot but what I do like about it is the radar service and separation I get from the very congested, not to say on a sunny weekend afternoon downright dangerous areas west of the zone and between LHR & LGW/LTN, when Farnborough/Brize can only give FIS due to workload. The very nice people at Heathrow have on more than one occasion continued to pass me traffic information even after leaving their zone along those busy corridors to the N & S.
