Further from TransPennine's £1 sale last week, there is now a nationwide Rail Sale consisting of 50% off 'advance' fares purchased between *today* and Monday 29th January for tickets dated between Tuesday 30th January and Friday 15th March;
https://greatbritishrailsale.nationalrail.co.uk/#/great-british-rail-sale
Away fixtures in that period include;
Maidenhead - 17th February (5 min walk)
Aldershot - 9th March (10 min walk)
Halifax - 12th March (10 min walk)
These tickets are available from the link above (or search 'Great British Rail Sale online), and not via third party apps such as Trainline (which is good, Trainline is bad).
Tickets are for 'advance' tickets only, valid for specific trains only. Additional discounts (Railcards) cannot be used.
*EDITED* to remove Ebbsfleet from the list as the 'strike week' is excluded from the travel period, even if trains to / from the destination are running.