It's a fair question; my guess would be that the GR1/F3 build up took place with the Defence Budget running at a substantially higher % of GDP, therefore there was more cash to go around, we were still in the Cold War so there was more of an urgency to re-equip (particularly wrt replacing the Vulcan and Lightning) and we had far more aircrew/Sqns/bases so it was easier to drop a Sqn from the front line to retrain (or simply transfer a numberplate). In addition, the Govt has really wanted to get out of 232 Typhoons so delaying the replacement of the F3 by allowing UK build slots for export made sound sense. Typhoon has suffered by politically inspired delays (from all 4 countries at different times) and by the "peace dividend".