If that's what the winner got for his money, I'd say that's a good buy. The "no omnibus" caveat is useful too, as I think they are really a separate project.
I don't think there's much of a problem with forgeries of this type of stamp (except maybe one or two of the very rare ones), and at £22, the risk of losses is pretty low.
Have you come across Murray Payne yet? Among other things, they publish a KGVI commonwealth catalogue - back copies are not too pricey on
ebay when they show up.