You will need to pay for your professional advisers - usually your solicitor and often a surveyor. Under the terms of the lease, you will usually also pay for your landlord's professional advisers. Obviously costs will mount if the negotiations are drawn out.
You usually negotiate a payment, based on current market conditions, to terminate the lease. If the local property market is weak, this could be substantial. Conversely, you might be able to negotiate for the landlord to pay you if the property market is strong and the rent on your lease is below market levels.
You may be liable to pay for dilapidations - repairs and redecoration - if the lease requires you to return the premises to their original condition.
You will also have other costs such as vacating the premises and relocating.
