Neil,
The Harrier is a fifty-year-old design. The Spitfire was only a thirty-year-old design when the harrier was introduced.
Quite correct however it would be better to have Harriers than no aircraft at all on our latest and most ex[pensive carrier which will be a white elephant until the American planes become available. It is a bit like buying a top of the range lathe or mill and not having any tooling for it or material to work on.
The Americans very quickly purchased all our Harriers appreciating their unique abilities that were demonstrated in a spectacular manner in the Falkland's War.
Eric