Sorry for delay, yes custom stock replied, bit of a slapped wrist for leaving it so long, was given a few DIY bits to try but if it really didn't fit to send it back. Apparently it should sit flush on back shelf of the stock, mine definitely doesn't!
So took the stock off, on my 2017 hw100k there is a ridge across the bottom of the action 29 x 3 X 0.5mm. Now, mine has no inlet in the stock to accommodate it, so there it sits and rocks on this ridge, with approx 2mm movement either end of it. Maybe an omission but a minor, annoying design issue?? Will probably Dremel it out. If I could work out how to attach a picture I would, paints a thousand words and all that, thanks.