Bakker doesn't appear to be well stocked in stores. You're best best for buying them would be online, probably through Amazon UK.
Ask SilentRoamer though, as he's in your area, or thereabouts.
Grimdark is released Quarterly, first edition was October 1st. Next issue is January 1st, but no word yet if The Knife of many Hands will be included in that one or not. Bakker claimed that the story was finished, so I'm hoping it will be included in that second issue of Grimdark.
Its an online only magazine and its $3 per issue.