Hi Fabi. Bad news I’m afraid; usually it’s in the terms of your lease that you have to contribute towards lifts (etc) even if you don’t use them. Very annoying but standard practice. The general policy is that the infrastructure cost to your block/estate is divided by the number of properties (not size) and billed accordingly.
It’s a method of “fair” billing; recent informed advice has been to make sure that when there’s consultation works make sure that the works are appropriate for the block/estate/property – e.g. that they aren’t overspecified and happen only when necessary, rather than too soon/when the previous works for the same area are still under guarantee!
Camden have now published a Service Charge guide explaining how they divvy up the charges: https://www.camden.gov.uk/ccm/cms-service/stream/asset/?asset_id=3414319&