The top prize is £5,000, though you can win bottles of whisky and smaller cash prizes each month. It's free to enter so it's well worth taking the time to select your squad.
There is also a prize for the mini league which ends up with the highest average points tally over the course of the season. Of course, a St. Mirren one has already been set up by Saints fan chico. If you want to enter it, visit http://britishfantasyfootball.theherald.co.uk and register your team. After it's all set up, click the link to joina mini league. The league's name is SMFC and the password is EET7E.
You can register your team at anytime, though I'm waiting another week or so to see what transfers take place :-)