Sometimes, the estate agent is paid by the landlord and so as the tenant you do not have to pay an agency fee. However, these costs are usually sustained by the tenants, who are asked to pay 1 month to the estate agency, on top of the other expenses - i.e. first rent and deposit.
To find an agent or a list of estate agents in your chosen area in the UK you should contact:
The National Association of Estate Agents
21 Jury Street,
Tel. +44 (0) 1926 496800