Passengers who wish to make a claim for out-of-pocket expenses or compensation following this disruption should contact British Airways directly in the first instance. If they are not satisfied with the response, they should refer their claim to British Airways' appointed dispute resolution service, CEDR. Dispute resolution services provide independent decisions on passengers' claims that the airline is contractually obliged to abide by."
That seems very commercially unwise for BA. The "contract" is of BA's making and entirely weighted towards the BA point of view, ie 'we don't owe nobody nothing for anything'. If all the dispute resolution contractor (selected and paid for by BA) is going to do is look at the BA contract and conclude people aren't entitled to anything more, not only do they add nothing to the situation (apart from pocketing their fee from BA) but are going to lead to a lot more hacked-off people, with their stories in the Daily Mail, etc.
BA were going round posting that overnight hotel expenses UP TO £200 for a double room (ie £100 each) would be reimbursed. None of the hotels around Heathrow normally charge such a low rate, and there were press accounts that on the weekend in question they were quoting four figure sums for a room for a night.