You do of course reach the point where you need to provide enough of an incentive for talented people to want to become MP▸ ’s in the first place. The annual salary is very low (£85k) compared with similar jobs people of the required talent can get in the private sector. Some form of perks for the job are necessary and inevitable, otherwise you simply won’t get MP’s that are good enough.
Whilst public money should not be squandered I personally have no problem with what current guidelines state in that if a first class advance is cheaper than the standard single that should be allowed, and indeed encouraged where possible as it does provide a better work environment.
I've long held the view that an MP's salary should be linked to the average salary in his or her constituency. Probably not a multiple of 1, but maybe 2 or 2.5 times average. This should keep MPs fighting for their constituent's economic benefit and (please) stop them all toeing the party line so much (particularly when they're members of the governing party(ies).