Royal Mail Post and Go machines A012, A013 and A014 will be attending Spring Stampex at The Business Design Centre London on 15-18 February 2017.
Each machine will vend the new Mail by Rail issue along with:
A012 the Machin, with a ‘Machin Anniversary 1967-2017’ inscription.13 January UPDATE by WhiteKinght on another post:
A013 the Locomotive design from the Heritage Transport set.
A014 the Machin with a ‘65th Anniversary of The Queen’s Accession’ inscription.
The Isle of Man postal service will launch its "Variable value" definitive stamps at Spring Stampex next month. The initial publicity shows 4 designs depicting "The Legs of Mann" and they look very much like "Post and Go" labels.
So far the publicity has not used that term so presumably the stamps will not be Royal Mail IAR labels but from another source - perhaps the same as the Irish "Stamps on a reel" (SOAR) (I'm only speculating here of course)
UPDATE 13 FEBRUARY:
Mail by Rail will be available from The Postal Museum from 15 February and from Steam GWR Swindon from 20 February with their respective additional inscriptions (or overprints or underprints, depending on who is describing them). At both locations only 1st class stamps will be dispensed.
Jersey Post has a new set of Shell designs available from 15 February, and Guernsey Post has a set of Lighthouses from the same date.