Mac, do you live locally to where you will be letting the flat out. I say this because i put my house i was letting out in the hands of a letting agent who has pretty much done no work on my behalf.
To this end i advertised the house in Gumtree, had a solicitor draw up a tenancy agreement along with a AT5 form and did everything myself. Within a week we had a young couple move in who provided references and deposit etc.
As long as you can arrange workmen to come out in an emergency and are happy to deal with the council tax and utility bills which is a doddle and only a couple of phone calls then there really is no reason to give an agent 10% or more of your rental.