I live in London, so no point in listing music opportunities here, and the OP correctly excludes big towns from this thread. To me, however, at this stage in the thread, the next question is - how many of those pubs and clubs in the lively/healthy music scenes you mention pay the band a reasonable fee?
As we, as a country, descend into austerity/recession/downright poverty, I'm noticing that even successful venues are absolutely penny pinching and some are offering bands what we consider a ridiculously low fee. We have turned down a few offers because they were well below our minimum fee, and we've received enquiries that quickly faded away as soon as we mentioned our minimum fee. That's all right by us - we're not desperate and there are still plenty of venues who recognise the quality of the band and are willing to pay more to have us.
We're not the kind of band who don't get out of bed for less than $10,000. We set our minimum fee so that we can pay for the petrol and end up with a little money to justify the whole exercise, but nobody's getting rich. And of course, a band's minimum fee for London and the Home Counties will probably have to be higher than elsewhere in the country due to higher costs all around (that's why I'm not mentioning actual numbers).
However, I find the trend very worrying. So what's the situation in your thriving areas? Are bands undercutting each other in order to play? Is the scene healthy enough to pay every band acceptably for a gig?