This policy from the BA web site may assist? -
If you are affected by flight disruptionA policy has been put in place outlining the booking change options available to you if you are affected by flight disruption.
This policy relates to flights operated by British Airways (mainline) and
BA Connect ('British Airways' flights), and to flights operated under a BA flight number by GB Airways Ltd, Sun-Air of Scandinavia A/S, Loganair Ltd and BMED ('BA franchise flights').
It does not relate to flights operated under a BA flight number by Comair Pty Ltd. Booking change options following disruption to these services will be advised seperately.
It applies to any passenger who holds a booking on:
a cancelled British Airways or BA franchise flight
a British Airways or BA franchise longhaul (intercontinental*) flight which has been delayed for over 4 hours
a British Airways or BA franchise shorthaul (European or domestic) flight which has been delayed for over 2 hours
You can choose one of the three options set out immediately below.
1. If you wish to travel to your original destination,
you may re-book on another British Airways or BA franchise flight at your convenience, subject to availability.
Conditions
The change in booking must take place no later than two weeks after the original flight.
Travel must be completed within ticket validity or within three months from the original flight, whichever is longer.
The return flight, if applicable, can be re-booked at the same time, and no extra fare is payable.
2. If you choose not to travel to your original destination,
you may re-book on a British Airways or BA franchise flight to an alternative destination, subject to availability, with any additional fare to be paid by you.
Conditions
The change in booking must take place no later than two weeks after the original flight.
Where the new fare is lower, the difference will be refunded.
Travel will be governed by the fare rules applicable to the new booking.
The return flight, if applicable, can be re-booked at the same time.
3. If neither of the above options are acceptable to you,
you may claim a refund of the original British Airways or BA Franchise flight, plus any parts of the journey not made which are on the same ticket as the original flight.
Conditions
The refund will be credited to the original form of payment
To discuss or apply any of these options please contact British Airways, the relevant BA franchise operator or your travel agent, whichever issued your original documents.
Contact British Airways
If your flight has been disrupted and you have already arrived at the airport, please proceed to check-in or visit the British Airways ticket desk.
*Intercontinental flights are those offering FIRST, Club World, World Traveller Plus and/or World Traveller travel classes.