If those prices are already in the UK, then they're OK, but if they aren't and you don't "need" the knife immediately, I'd recommend looking around some more. In the (hopefully) near future, when the second DMDC run is completed, you may be able to order them from the Scrap Yard store for $90/ea + shipping + UK taxes/fees.

All things being equal, I like the S6 better -- the handle fits my hand better and the balance is outstanding. However, it's 2-inches longer than the DM (1.5-inch more blade and 0.5-inch more handle), so if size is a consideration, the DM may be a better choice for you.