Barry,
Excellent find! If it had been built, and had it of worked (a big if) the flying wing HP.117 could have been an incredibly efficient airliner, perhaps in hindsight its what Concorde should have been. The HP.119 confirms that HP was planning a scale demonstrator, perhaps the HP.130 was a product of the failure to get the HP.119 of the ground?
In fact the more I look at the design lineage it seems like the HP.130/135 were an effort at a more conventional boundary layer control aircraft than the earlier flying wing HP.117/119. With that said, in its latter configurations the HP.117 acquired what could be described as a fuselage, so perhaps the HP.135 was a natural evolution?