Hi Laura, I have just registered as a childminder as of May this year.
I made my first enquiry in December 2011, and had to wait until February to get put onto a "briefing course", which is a 3 hour introduction to childminding. Then I did a one day a week course for 4 weeks, at my local college. These were both free, as my council covers the cost. I also had to complete a 2 day Paediatric first aid course, a CRB check and a doctor's check, which in total cost me roughly £100.
Unfortunately, being a qualified teacher doesn't help you at all, unless you are first aid qualified already, and I suppose you will have a current CRB check. But you will still need to complete the courses.
I am in Kent, and as I understand it different counties do things slightly differently, not sure about Coventry. Also be aware that all the guidelines for childminders are changing from September so if I were you I would wait until after then to get started. As it is, I will have to go on a course to get updated in September!
One other thing - I thought I could get work fairly quickly but I'm actually sitting on Jobseekers while I wait for enquiries, and I have been fairly proactive in advertising myself. Don't expect to get started straight away!
Hope this helps, PM me if you need to know anything else.