MPs' Expenses

MPs are at it again, claiming that the rules governing expenses are too onerous and that the rules requiring them to only have small apartments, rather than the previous lavish mansions that they had under the old regime, is "anti-family and not acceptable".
There is a simple solution to the problem:
Civil Servants on Grades 6 or 7 earn approximately the same salary as that received by MPs. Why not simply use the same rules and expense scales that would be applied to these civil servants in the event that they are posted away from home on detached duties?
After all, they are the people who effectively determine the Civil Service pay scales and expenses regime, so surely "What's good for the goose is good for the gander".