Hi
Have you tried the Makaton website?
http://www.makaton.org/ If you let them know your address they will give you a list of tutors in your area.
Do you specifically want to do Makaton?
Signalong is another popular signing method
But BSL is the type of course you are likely to be able to do at a college.
If you have no luck perhaps you could get in touch with a speech and language therapist in your area who may be able to point you in the right direction.
PS The Makaton Nursery Rhyme video with Dave Benson Phillips is very good, and you can pick up alot of signing from that
Good Luck
Jo