The comment on the X1, Miles M1 is accurate. Miles were forced to hand over their supersonic expertise as part of a technology exchange. The Americans then reneged on the deal and refused to reciprocate claiming their technology was a state secret!!!!!!!!!!!!!!!!!!!!
Their is no doubt that Miles were screwed and would have been first through the sound barrier if the government had given them the support they deserved.
A huge amount of American post WW2 technology was stolen from the Germans. Radar, jet engine technology, swing wings, ejection seats, etc etc etc all came from the UK.