In my case, Lydna Watho claimed a total of £144,615 in 2007/8. The estimate for the constituency population from National Statistics (Excel spreadsheet 2.8MB) is 82,047. This works out at £1.76 per constituent - somewhat higher than the national average of £1.28.
This is the letter I propose to write:
Of course it is possible that MPs don't get sarcasm, but I think it would be entertaining none the less.
Dear Lynda Watho,
I understand that the salary you are paid for the post of MP for Stourbridge is only £63,291. As this is only two and a half times the average wage for the UK, you must be very short of money. I see that you last year you claimed over £144,000 for your expenses.
Some of these expenses I can understand, but others look a bit strange. None the less, this way of bumping up MPs wages seems to not be transparent and will inevitably bring parliament into disrepute. I therefore enclose a cheque for my share of these expenses, and hope that you will use it appropriately, such as putting it towards the purchase of a second house, or something similar.