Rang up today to use my booking that had been placed on hold, as expected although I was told by several agents I could book for any dates within 2 years from ticket issue without charge so long as the new booking was in R (the original booking class) that proved to not be the case and 31/12 was being enforced. I am happy to add a data point though to note that bookings that were placed on hold, are also eligible for a refund.

So the refund policy (voluntary) covers standard bookings, bookings that were converted to vouchers and bookings that were placed on hold. I wasn't expecting the latter but glad it's happened none-the-less, the cash is better in my pocket.