Hi Peter. JM Lab is a great choice (they prefer to be called "Focal" these days). If you don't want a sub, for a room that size and the possibility of the long wall positioning, I think the Divas would be perfect. The Divas love having some room to their sides for good bass integration and it is very hard to beat their imaging since they are so narrow. great speaker. You will only be disappointed if you don't work at setting them up properly - which means experiement with their placement. Sometimes it only takes a couple inches to make them go from good to great.
I prefer the JM Lab sound over the B&W (I currently own some N804 as well as my JM Lab 926). It boils down to the JM Labs being revealing and the B&Ws being ruthless.
Arthur