I think the big problem for the UK compared with other European countries was that we tried to do too many things in smallish quantities.
The other end of the scale was Sweden, who, first with Viggen, and then with Gripen, decided they could only afford one fast jet programme and made it as versatile and effective as possible.
A problem is that early on, the aircraft were not capable of doing multiple roles. The mission systems were too bulky. So at best you could have one airframe with multiple different permanent equipment fits.
Example, F-101 (F-101A fighter-bomber, F-101B interceptor, RF-101 photo recon). Also the Viggen (AJ37 fighter-bomber, SF37 photo recon, SH37 maritime patrol, SK37 2-seat trainer, JA37 interceptor).
A related problem is that there was no high level individual or command in charge of close air support type missions. All the air staff thought about was interceptors and strategic bombers. Fighter Command and Bomber Command, no "Army support command" or whatever you want to call it. To use the American names, the UK had
Air Defense Command and
Strategic Air Command, but not
Tactical Air Command. The various Air Forces (RAFG, NEAF, FEAF, etc) didn't have anyone making sure they had the right types of aircraft that they'd need for Limited Wars or close air support of the BAOR.
Then comes Sandys and the 1957 DWP. Now, the point defense interceptor is dead. Replaced by surface to air missiles.
Fighter Command loses their minds, because all they've ever thought about was point defense interceptors.
They don't see the different kind of interceptor you need to address bombers carrying cruise missiles, a mission profile the USN and RN have been particularly aware of for a while and call BARCAP. Barrier Combat Air Patrol. This mission requires really long flying range, because you want to be able to shoot down the bomber carrying the cruise missiles before the cruise missiles are launched and so your multiple hour patrol is going to be a couple hundred miles away from the UK. It also requires long range radar and missiles. It also effectively requires airborne early warning radars due to the curvature of the earth, until people figure out over-the-horizon radars.