John Douglass's reply:
Try contacting your local Music Hub or music service, you should be able to find this with a Google search.
In addition you can contact schools directly but the school music teachers are often very busy. It may be worth finding the names of the other instrumental music teachers in the school as they will be able to give you some guidance, and in addition, if a vacancy comes up, the school music teachers are quite likely to ask them to recommend someone.
This is probably a good time of year to make contact as the schools will be trying to sort out staffing for the next academic year.
In addition you could offer some, one - off workshops as a way of making contacts and getting yourself noticed.
You could also try Further Education colleges that run music courses.
Also remember you will need to be CRB checked.