Hi Lisa I DJ bit in Brum lol
What I would say is:
Ask the venue if they have a resident DJ (I act as a resident for a couple of venues)
Ask your family and friends if they know anyone
Do not get one off the internet or the yellow pages - if a DJ is any good they dont need a website or an ad costing several hundred pounds
When you book the DJ make sure you tell them any specific songs or types or music you want played, if they are any good they will make sure they have them or get them for you
Have a good night!