10% discount - GB Airways
https://www.heathrowexpress.com/gbairways/Tickets.asp

10% discount - JAL
https://www.heathrowexpress.com/jal/Tickets.asp

15% discount - ANA
https://www.heathrowexpress.com/ana

25% discount on paid First Class
Use the code STYLE

Plus for Amex holders:

20% Amex discount on HEX/GEX

The Heathrow and Gatwick Express are offering American Express Cardmembers 20% discount when booking on www.heathrowexpress.com/amex or on www.gatwickexpress.com/amex

Offer Valid 1 March 2008 - 13 April 2008

Terms and Conditions
To receive this offer, purchase must be charged in full to any American Express® Card.

Offer valid between 6 March and 13 April 2008. 20% discount available on pre-booked Express Class and First Class single and returns only. and booking dates are between 6 March and 13 April 2008. Not valid in conjunction with any other offer or discounted railcards