Double Zero,
You have already pointed out that the production line is long since closed, thus second-hand would be required. How much usable life is likely to be in any airframes (and engines etc.) that the USMC would be prepared to hand over (their older ones?) once they get their shiny new F-35s? Surely not that much? However it might be enough to keep us going for a few years until the price of a F-35 comes down into our affordable budget. Personal view is that if 60,000 tonnes of diplomacy is what the UK wants, I think that buying into UCAV operations is the longer term solution, so anything else (F-35, F-18, others) should be considered a stop gap until then.
QA