The main lines through Reading station will be closed 14+15 October to carry out further testing of overhead wires for electrification.
This will result in various bus substitutions to complete journeys to and from London to some popular destinations on here such as South Wales, Bath, Cotswolds, Devon, Cornwall etc, as well as on Cross Country.
Not all details have been published yet, although a revised timetable is now available on the National Rail site for 16 October.
Tickets already, even Advance ones normally tied to specific trains can be changed to 13 or 16 October, or refunded without fee.