That surprises me too. I'm surprised Festool would agree to it and to me it sort of hints that they might be altering direction somewhat. Hard times? It's not as though Screwfix is a new distributor and as part of the same group as B&Q, they would always have had access to any brand they wished, in theory, as they are certainly not limited by buying power.
An odd choice.
As for Screwfix, what wins them my business fairly often is that they are open on a sunday and if I need a box of screws, I'm always going to go there instead of B&Q. The staff in B&Q are absolutely useless in the main, thats if you can find someone at all, whereas in our Screwfix branch, I've found them quite helpful. Although not amazingly knowledgeable, they know their way around their own stock and the general terms for things.