Evo, cant say I favour your route. The direct route I have in mind is clear of Blackbush anyway, and going overhead means getting very close to the LHR Class A airspace, then leaves me a bunch of danger areas to dodge. If I went above 3000ft QFE I'd be clear of the MATZ anyway.
I dont know, maybe I'll go direct to Southampton and fly aorund the Needles instead.