We have different sized flats in our block, why should we pay the same service charges?
Your lease is your contract between yourself, the freeholder, and any other intervening parties. If that contract effectively states that all 32 flats will pay the same proportion of service charges, then that is the contract which the original lessee accepted when the lease was signed, and which you accepted when you bought the flat.
The natural inference is that, at those two times, all parties considered that the fairest way to apportion the liabilities was on a per unit basis and not a floor area basis. Many other flat development schemes have followed a similar principle, I accept that there are also many other schemes which have apportioned service charge liabilities according to rateable value, or floor area, or some complicated formula as to usage of particular services.
It is not unusual for the owner of the smallest apartment to feel unfairly treated when service charge proportions are not based on floor area or size. It is a problem which gives rise to many complaints and disputes.
There are provisions in the Landlord and Tenant Act 1987 (S.35 and S.37) for applications to be made to an LVT for a variation of service charge proportions in certain circumstances.
The LVT has discretion and is not bound to order a variation. Possibly more important from your point of view is that, if you were successful in challenging your proportion through those statutory provisions, the lessees who would then find themselves having to pay a larger proportion than is contained in their contract (their lease) would also be able to apply to the LVT for compensation based on the financial damage they will suffer in the future for having to pay more than they thought they would have to pay when they bought their flat.
The short answer to your query is that the possibility of mounting a challenge exists, LVTs would be overwhelmed with work if such a challenge was considered to have a strong chance of success, it is likely that a successful challenge would then be followed by applications for compensation, and you would have to have a very good explanation of why you bought this flat in the first place, knowing of the problem, to stand any chance of persuading an LVT to exercise their discretion in your favour.