Chefs like Gary Rhodes attended local FE colleges and then apprenticed themselves to a chef from a great restaurant kitchen.
I've attended lots of courses around the UK and Ireland, but most of them have been short courses, lasting no longer than a week, and they have all been VERY expensive!
I would think that Bristol would have a reasonable selection of FE colleges for you to start your search.
If you are older and intend to pay for your own courses, I'm not too sure what to recommend.
I attended a six week, intensive course at LCB in Paris, many years ago - but I know that course would be sufficient to allow you to claim to be a chef!