Your lease agreement should set out what your share of any service charges should be. It is unlikely that there will be a fixed charge, so it will be calculated based on a fixed percentage (your percentage should reflect the share your leasehold represents within the whole freehold property) of the total costs. This will include repair, maintenance, management and insurance of the building. It may also include an amount which goes into a reserve or 'sinking' fund so that there is a money available for major works, such as repairs to the whole building.