To add to Archemedes' comments, the contractual position is complicated by the fact that it (the contract) was all geared around national workshare and that, thus, to reduce numbers, all nations have to be in agreement; this doesn't take into account any cancellation clauses levied by industry. The result of all this is that, in basic terms, the UK could reduce unilaterally, but would still have to pay the partner nations for 232 aircraft's worth of the bits they provide plus any other cancellation fees. As I understand it, the Germans and Italians would gladly reduce numbers, but are being held to the quadrinational agreement by Spain, whose TUs would probably revolt in the event of a reduced workshare. This as explained to me by a severely harrassed Typhoon IPTL last year. Hope this points you in the right direction.