In fact, the Germans (as explained to me by a senior EADS bloke and a Luftwaffe 2 star) are actually looking at needing each and every one of their Typhoons - perhaps even some of their options, because they're looking at a much reduced Tornado fleet.
The first to blink and request a reduced offtake will be faced with MASSIVE penalties - such that it would be cheaper to take delivery of the aircraft, line them up, and pull them to bits with a JCB.
And while we may be buying more Typhoons than we need (the 137:232 figures were predicated on a seven squadron force) we're not buying a lot too many, and the 'spare airframes' could simply be used to further extend the OSD, to fulfill part of the moribund FOAC requirement, or perhaps even as a replacement for some or all of the JSF buy.
Bear in mind that despite the announced closure of Leeming as a FJ base, no-one has officially reduced the requirement from seven Typhoon squadrons, so theoretically we still need the full 137:232 figure.
And 232 Typhoons gives you a frontline force of 137, as we know.
"......the 232 aircraft being procured will support an active RAF fleet of 137 Eurofighters. These may become known as Typhoons in RAF service, as they already are on the export market, though this has yet to be confirmed officially. The 137 active aircraft will equip seven front-line squadrons (15 aircraft each, plus four in the Falklands), an Operational Conversion Unit (OCU) with 24 aircraft, and an Operational Evaluation Unit (4 aircraft). These units will share nine further aircraft which will be categorised as in-use reserves (one per squadron and two with the OCU). The remaining 84 aircraft will be rotated in and out of service, covering attrition and spreading flying hours to enable the aircraft to reach its scheduled out-of-service date.”
That pretty well directly repeats what was in Hansard at the time.
I'm sure that you don't need 232 Typhoons AND 150 JSF/JCA to have the 84 deployable FJs that are the current planning assumption.
Interestingly, the 137:232 Typhoons will be replacing 87 Tornado F3s and 46 Jaguars in seven squadrons...... 133 aircraft!