a lot of people don't seem to realise changes like most of the examples posted are as a result of the airline's standard commercial policy regarding disruptions and delays, rather than special one-off favours....

if a shorthall flight is delayed by 2hrs+, you can change it or get a refund
if a longhall flight is delayed by 4hrs+, you can change it or get a refund
if your original flight number is cancelled, you can change it or get a refund

the new flight must be in the same cabin to the same destination if you change to a date up to 2 weeks either side of the original flight.

the new flight must be in the same fare class to the same destination if you change to a date outside 2 weeks of the original flight.

a public version of the policy can be viewed here:

http://www.britishairways.com/travel...y/public/en_gb