This locked topic will be updated with details of the dates for which Advance Purchase tickets are available for
GWR▸ services. It is worth remembering that sometimes a walk up return ticket can be cheaper, or only slightly more expensive, than two Advance singles and offer greater flexibility so it is always worth checking both prices and not automatically going for an Advance ticket which restricts you to a chosen train. Also note if travelling at weekends and wishing to go first class, it is sometimes more economical to buy a standard class walk-up ticket and upgrade to Weekend First on board.
February 2018 update: As the GWR website now gives regularly updated booking horizon dates it is now simpler to direct you straight to
their page, rather than repeating the same thing verbatim here.