Not really BA in my case, but it was an BA/AA itinerary, LHR-MIA-PLS, in CW on BA miles. Our MIA-PLS was cancelled and it was the last flight of the day and AA put us up in the hotel at MIA, gave us amenity kits and food vouchers (can't quite remember how much, $50 or $75 each I think) and put us on the first flight out the following morning.