Regarding divisions,
In most tourneys it will be broken down into divisions (i know nspl is div 1-4 not sure on masters) you generally enter at the division you think your best suited to. usually starting at the bottom and working your way up. the top teams promoted and the bottom teams relegated to the division below (obviously not div 4)
There are a few tourneys scattered over the uk, Masters and NSPL being the main sanctioned events, with freekz in south-hampton and a few others scattered around.
The masters and NSPL also run KOTH leagues (king of the hill) which is for entry level players. I know the NSPL is split into rookie and novice, with the chance of being promoted. the proto KOTH (nspl) is ran the day before NSPL, and the masters the same day as the main event.
Hope this has helped
Dave