That is a very handy sum isn't it mrsmopp, more than most people can ever hope to earn in a year and far above the 'average' wage.
I wonder if Mr C could be persuaded to donate the rental income, which he doesn't need, to a housing charity or similar. So far as I know, he doesn't pay rent on number 10, or chequers, so he's quids in, particularly given the ridiculous way in which house prices are rising in London.
I still believe MP's should be paid more, similar to head teachers and GP's, or managers in industry etc. Their main home should be in their constituency, and some form of basic accommodation provided for them when they're in London. Expenses should be monitored in the same way they are for other public servants. There are set amounts for meals, petrol, rail/air travel and alcohol is never claimable.