However, at the risk of being called a cynic, I notice none of this affects the MPs' pensions schemes
I agree entirely - load of thieves they are from whichever lot are in power.
Tim, will have to leave the valuation question as I just don't know - I still would stress that they are professional and independent enough to apply their judgement without pressure as actuaries, rather than being tools of management's will. Certainly management will present data as they see fit to prove their point, but I still doubt that even with any management manipulation that it would materially change the extent of the underfunded nature of the scheme.