Jig Peter - I have Damien Burke's more recent TSR2 book and the story of "which airfield" is rather different in that one. Basically - Vickers in charge (and they were - no doubt about that), wanted to use Wisley (as with Valiant, VC-10 etc.), English Electric wanted to use Warton (longer runway, clearer airspace), but once both companies were merged into BAC the Vickers component agreed to use Warton but were overruled by... Ministry of Aviation, who chose Boscombe Down. This remained the case for a year or so until delays meant BAC(Vickers) suggested Wisley again (to save a month of dismantling/transporting to Boscombe/reassembling first aircraft), and Beamont at BAC(EE) objected as engine problems and weight growth meant reduced safety margins at Wisley and any immediate re-land case would force use of Heathrow (with heavily populated surroundings). So back to Ministry Men's choice of Boscombe. McLelland version seems to be just Beamont's version of events.
Reading Burke's book it seems the greatest blunder of TSR2 was not cancelling it sooner, or perhaps believing RAF when they wanted mach 2, rough field, kitchen sink etc. all in one jet.