Deliverance,
Good points, and thank you. Howeverrrr...
The discussion over any UK boom refuelling capability needs to be an informed one, not just 'oh, now we could do this'. The UK procured the RJs and the Sentry fleet without buying a boom capability, so any subsequent boom buy would need to be justified against the F-35A requirement. The problem there is that the best way to AAR an F-35A, as far as I have read, appears to be via probe and drogue. The boom system was driven by the need to transfer large amounts of fuel to large aircraft that might have problems hitting a drogue - and it's an insanely great system for those platforms. But for groups of smaller tactical aircraft that can't use the boom system's higher flow rates (and I don't believe that an F-35A can) then a multiple drogue system should be a better bet.
But then we get back to the costs of fitting the A model with the retractable drogue. I think (just my view) is that this will end up as a budget drill, rather than a 'needs based' assessment. What would be especially unfortunate is a situation where the F-35 'budget' ends up getting raided to update the RAF's tanker fleet.
Best regards as ever to all those crunching the numbers,
Engines