Dunno if any of you know but there is a free to play fantasy football site for the SFL leagues. Just go to:
http://www.fantasylowerleagues.co.uk
I have ran this site for a few seasons now. It has all your usual features such as picking a team of 11 plus 4 subs, captain who scores double points, create your own mini league etc.
Check it out :) Only 1 week to register and pick your team before the season start.