Martin,
The list you put up shows 5 fleets capable of ground attack (Harrier, Jag, Tornado, Buccaneer and Phantom).
AD has two types (three if you count Sea Harrier) - Tornado & Phantom.
This must have been ridiculously expensive, to have so many fleets with overlapping roles.
Now there are two types, and one to come (i.e. F35) that will replace the Tornado. Seems like a more affordable proposition to me. Maybe more frames in more squadrons required, but not more types.