Woff,
You're factually incorrect. The figure of 232 Typhoons was arrived at 'not by adding up the F3s, Jags and Harriers' but by determining the number of aircraft required to maintain a seven squadron frontline force (137 active jets, if I recall correctly) out to the OSD. These seven squadrons were, it's true, expected to replace the F3 and Jag forces (which then stood at nine frontline squadrons, but have since reduced to seven).
95 'spare jets' for attrition replacements and to cover maintenance etc. is by no means an extraordinary proportion, especially over Eurofighters long planned lifetime. Any reduction from 232 aircraft will mean either a smaller force, or a reduced life.