It's clear that Skylon, or in fact any other muted system is a way of keeping people interested in REL. The only interest is in developing the SABRE engine, and I think that that is completely the right thing to do.
Having read a lot of the blurb and seen the talks too, my understanding is that there's no point creating an engine without having a feasible concept spaceplane to stick it on otherwise how would you know what the engine should look like, how big it should be, whether it could actually get something into space?
Hence Skylon isn't necessarily their business and the end vehicle might be different, but it seems to me that there would need to be a very good reason for ignoring it altogether.
Regards,
Tim