Definately don't pay them. I work for a different letting agent and we do not do this. It is deemed to be an unfair clause and one of my friends had exactly the same problem with leaving the 2 year contract (which they love to tie you in to) and I wrote a strongly worded letter to them stating that it was an unfair clause, they could not charge a tenant the commission for a tenancy and that if they wanted to try to get the money they could take her to court for it. Every time they have to take someone to court it costs them enough that they do not bother. After I had written to them my friend did not hear another word from them.
Don't pay the commission
Definately don't pay them. I work for a different letting agent and we do not do this. It is deemed to be an unfair clause and one of my friends had exactly the same problem with leaving the 2 year contract (which they love to tie you in to) and I wrote a strongly worded letter to them stating that it was an unfair clause, they could not charge a tenant the commission for a tenancy and that if they wanted to try to get the money they could take her to court for it. Every time they have to take someone to court it costs them enough that they do not bother. After I had written to them my friend did not hear another word from them.
DON'T GIVE IN