it's remarkable how popular the BM has become in just the last few years. I'd leave it until early Dec. and sail in. No wonder why it's thus: 95% flat, great setting, superb changing and a good quality memento. And a top start to Spring Marathon prep.
if looking for an alternative, the Four Villages half Marathon at Helsby is usually the same weekend: well organised, popular, well resourced H/Q, undulating and attractive course and a distinctive medal for finishers. Fills fairly quickly too, though.