I studied German for five weeks in May 07 with the Goethe Institut in Berlin. It was an excellent course and the teaching was of high quality. Of course you're presumably not looking to do it in Germany but I imagine the quality will be similar wherever you do the course. I did find that the cost was pretty high, though (although I suppose you get what you pay for).
I'm currently studying German at University as a mature student (called something else these days, 'Open Learning Programme') and it seems that I could have studied there as a complete novice in German. You may find that a local college or Uni (if there is one in Bolton) also do German courses, although I struggled to do a course where I used to live in Kent as so few people apparently wanted to study German.