Terminating agreement with management Agency

Tenancy Types and Management

I would like terminate the agreement I have with the management agency I am using to manage my property. I thought I would have to give them a month or so notice but because they found the tenants for my property they are now informing me that whenever I decide to terminate my agreement with them I will have to effectively pay an exit fee. I'm afraid I did not read that clause in the agreement. Is this a fair charge? Is this like a finders fee?

This is the clause :

1. 3.23 terminate this Contract during a fixed term tenancy arranged by us, you agree to pay a charge equivalent to the balance of any full management or rent collection fees set out in this agreement that would have been payable during the currency of such tenancy (provided that we are not in the breach of the Contract).
2. 3.24 terminate this Contract following a successful letting of the property by us and the existing tenant remains in the property under either a statutory periodic tenancy or enters a new fixed term tenancy agreement with you, you agree to pay a fixed charge equivalent to six weeks' rent +VAT (provided that we are not in breach of the Contract).

Thanks for your help.