Blocks of flats of any size will usually have a service charge attached to them. This include all manner of things that are required for people to live there, including general maintenance, larger repairs, cleaning costs, heating costs, the costs of any building security concierge, and more. The cost of service charges will vary depending on the individual block of flats.
The service charge will usually be payable by the landlords of the individual flats. If a landlord rents out a flat, it might be payable by the tenant who lives there, but usually the landlord will take responsibility for the service charge. The cost of service charges on a blocks of flats can vary enormously depending on where the flats are located, the condition of the block, how old they are, and whether or not there are added extras such as a concierge service. If you live in a more luxurious block of flats, the service charge will probably be higher.