I had a brief chat to one of their folks at the stand in Farnborough. They've done some demonstration of the core technology (the precooler/heat exchanger without frosting) and they're working on coupling that with a small engine, or something like that.
As a bit of background, the underlying work comes out of the still-classified HOTOL project in the 80s, so it's not exactly new, it's just been hobbled by previous attempts to get it working.
Us folks who play KSP love it. :o)
