Well, it seems that PPP are no longer selling e-books directly via their site as far as I can tell from the lack of "add to basket" on their listings any more.
However, for people who are presumably neither Australians nor UK shoppers, the follow-up series sale books have now dropped to the
discount price at Books on Board, which has them DRM-free and with their ongoing 40-50% off sale has them at prices ranging from $2.34-$4.77 plus the extra Reward Bucks.
I went and read the 1st one of these and Greenwood's other freebie series and I'm going to pick up at least the $3.40 or less sale titles Real Soon Now.