It is amazing how poorly London is served for GA traffic, for IFR.
A coordinated transport policy would have a GA airfield nearby, with an ILS at both ends, good transport links, and operated as a centre of excellence for all GA up to bizjets.
Instead, the light jets fly into places like Luton (where the entry level to touch the tarmac is about £500) which have better transport links into "London" than Biggin Hill