National Express are offering a 10% discount from their "lowest Advance Purchase products"[1] booked on their website before 31 July this year.
http://www.nationalexpresseastcoast.com/Special-offers/Online-discount/
[1] According to the page, this is "excluding trains arriving into London before 1115 or leaving London before 0929 or 1555-1901 inclusive (Mon-Fri). Lowest fares are on sale on all trains at the weekends."
http://www.nationalexpresseastcoast.com/Special-offers/Online-discount/
[1] According to the page, this is "excluding trains arriving into London before 1115 or leaving London before 0929 or 1555-1901 inclusive (Mon-Fri). Lowest fares are on sale on all trains at the weekends."