The Poetry School. They run day workshops throughout the UK as well as courses running for a whole term (or longer) and interactive online courses with between 3 and 5 sessions. Stand-alone downloadable courses are available at reasonable prices. Another route would be to take a Creative Writing course with a University, including the Open University who run short courses as well as Level 2 and 3 courses as part of a degree (though there is nothing to stop you taking these as stand alone).
Have a look at what there is, gather your brochures and download anything interesting from the internet then go through it all and decide what is right for you and your budget. But hurry, places are getting booked up quickly already!
What will you be doing to improve your writing this autumn - let me know.