Perc
I think the reason for F35B is mostly because it doesnt need a catapult, and that apparently saves quite a bit of cash. The fact that it completely cripples capability compared to the C is, of course, not really relevant. Also, to be honest talking to various people I can't help but feel there is a bit of number 3 there as well.
Having said that, I still think that F35B is better than Rafale or (god forbid) navalised Typhoon. The stealth just adds another capability to the UK armed forces. Just so long as the target is susceptible to 2 x 1000lb and not too far away! The C would be soooooo much better and apparently its not too late to change!