I am afraid that I cannot answer...: 20 Feb 2012: House of Commons debates - TheyWorkForYou
Taking Squirrel 41's question literally rather than rhetorically, as of 20 February 2012, Peter Luff didn't know the answer, as the above link confirms. His answer also referred to the carriers as well as the aircraft.
A number of F35 customers, such as Canada, Australia and Japan have become nervous about timing and pricing since the US slowed down acquisitions last month. As the price depends upon the production runs, which are dependent on both US orders and export orders, I'm not sure anyone anywhere knows the answer to this question.