Can't you purchase this ticket from the usual machines where you are, here in East Anglia the Anglia Plus ticket is available on the ticket machine, in fact its on the home screen as a popular ticket, however I dont think you can buy the 3 in 7 version though, perhaps someone will correct me if I am wrong
For reasons unbeknown to me, two part rover tickets seem to be impossible to buy from TVMs, on train or even from ticket machine equipped barrier staff.
Causes me the occasional problem when my local station (LOC) ticket office is not open on a Saturday morning and I wish to travel on the 0806 Tpex service to MAN, as the guard will accept my undated retired priv pass as an authority to travel with a "buy your tickets at your destination/when you alight", trouble is I then have to get through the Northern barrier Line at MAN to do so!
What makes it worse, is that also for reasons I don't know there appears to be a "bug" in Scotrail's ticketing system which prevents advance issue of these tickets - the start date of the ticket always defaults to the day of purchase. Not a problem for Virgin, EC, Northern ticket offices though as I have successfully bought the same rover in advance from all those offices.
I have to agree that there should be either a PERTIS machine at all penalty fare stations, or at least a button on the TVM that gives a Pertis type Ticket where your intended ticket/destination/method of payment is not available.
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To quote from the authoritative document, the NRCOC:
3. Where the full range of tickets is not available
If you cannot buy an appropriate ticket for the journey you want to make because the range of tickets that is available at the station from which you intend to start your journey is restricted, you must buy a ticket or Permit to Travel before you travel that entitles you to make at least part of the journey. Then you must, as soon as is reasonably practicable, buy an appropriate ticket to complete your journey. In these circumstances, you only need to pay the fare that you would have paid if you had bought a ticket immediately before your journey. The price you will have to pay will be reduced by the amount paid for the ticket or Permit to Travel.
(Note that this applies with or without a PF area)
And that wording should be on or beside each TVM, so that passengers know exactly what to do - of course that wouldn't suit the likes of Northern, FCC, SWT at all!