Trislander,
Popham/Denham:
Route just north of EGLK as if you were going around the outside.
Talk to 119.9, 5 mins before the zone (mininum)
Ask for SVFR, routing Bracknell - Burnham (as in a "pass your details" message)
Chances are you'll get a clearance not above 1000 or 1500 on London QNH (depending on rwy in use at EGLL).
There are plenty of FL areas as anyone who's actually flown the route will know
For comparison purposes: going from Blackbushe to Elstree, using that routing through class A, saves about 5 mins compared to going around outside Booker in an AA5A/B.
Don't forget your minimums (viz)
Valid IMC = 3 kms to accept SVFR
No IMC = 10 kms to accept SVFR (I think)