Originally Posted by Cymro

My educated, but not "qualified" view, is that it will depend on what is reasonable in all the circumstances.

BA's lack of action and guidance certainly plays a role here.

My view is that there is no strict financial cap - but clearly if the Conrad is going for £150 per night, it's not reasonable to stay at the Park Lane Hilton for £700 when someone else is paying. So a lot depends on what the OP actually did. If the filters were used, that could exclude a lot of options, but as even the Leonardo and the Park Inn are 4*s with a rating >8.0 on booking.com, I think that's frankly the least that anyone can be expected to do.

(I'd consider both of those to be three stars with a rating of about 7/10).

If, in that context, those were the cheapest and closest options to Heathrow (and not "London") then it seems as though he has mitigated his loss from BA's breach as much as anyone could. If he has done that, the £200 cap from BA is arbitrary and not actually documented in the contract.

If, however, the OP usually stays at Premier Inns near the airport but decided he wanted a 5* in Central London for the night, even though he could have got something decent and close to the airport for much less, £200 is frankly generous. I'm not suggesting that it is the case, but £295 would not be recoverable in those circumstances.

In general, in the absence of guidance, I'd suggest that the OP's obligation is to find the cheapest acceptable accommodation, in line with his usual travel style or expenses budget, in a reasonably close location, with a modicum of effort (maybe 10-15 minutes). He doesn't need to document that in any great detail, but should be able to give evidence to that effect.