A friend and I have just signed a publishing deal and need a good manager. We've got no clue where to start looking because we're from Nottingham and everything seems to happen in London...
Good management is by no means exclusive to London (or any other part of the world) so your manager has to be London based. The advantage of London based management, however, is the fact that London is at the heart of this country's music biz and close to most of the companies you may intend doing business with.
The key to good management is trust. You need to have complete faith and confidence in your manager's ability to make the right decisions for you. Accessibilty to your manager at short notice is crucial so if you're in Nottingham. a London based manager may not be the best thing.
Effective management is about contacts so someone with a proven track record is worth considering. Also familiarity with your genre of music is important ,so you might want someone already managing acts in a similar area to yourself genre-wise.
Most importantly, always have a firm legally approved contract in place defining the duration of your working arrangement and what each party expects to get from the relationship BEFORE YOU START!