it seems so strange that an aircraft so advanced was being transported on a lorry from what appears to be the stone age

Thats because in British transport terms it was the stone age:) I’m afraid that while being able to design a wonderful looking machine as the TSR2 was, we couldnt get our heads around prime movers. Hence when driving the motorways of Britain you see nothing but Scania, DAF, MAN, and Volvo trucks.
By the time we could design a half decent heavy goods vehicle,that did not have its roots in steam powered vehicles, the market was lost… where have we seen and heard that before eh?