A friend of mine had the bad luck of being at Heathrow during the chaos on Tuesday evening (August 3). His flight to Madrid (BA 462) was eventually cancelled and he ended up spending the night sleeping on the terminal floor.
He is now in Madrid, but has been without his luggage for close to 72 hours. If I am understanding him correctly, he was not offered a hotel voucher that night at Heathrow and has yet to receive anything from BA for expenses relating to his lost/misplaced bags. If there is anyone on this forum who has been through a similar experience with BA and would like to offer advice about what compensation is reasonable in this situation, it would be appreciated.

1.Will BA reimburse him for the hotel he had guaranteed in Madrid on the
night of August 3?

2.Will BA reimburse him for phone calls to his family in the US and to his friend
in Madrid advising that the flight was cancelled ? What about his phone
calls to cancel hotel reservations in Malaga while he is stuck in Madrid
waiting for the bags to arrive?

3.Assuming they eventually do find his bags, will BA reimburse him for
toiletries and clothes during the 72+ hours he was without his belongings
and for the return taxi trip to the airport to pick up the bags?

4.Is there any compensation for the general inconvenience of having to
rearrange his holiday and spend extra days in Madrid waiting on BA to find
his bags?

Although the flight was cancelled ostensibly for "weather-related reasons", from what I have read here I believe that at the time it was cancelled (around 22:00) the worst of the weather had been over for hours and other carriers were managing to depart. The cynic in me suspects that BA could have flown this one if they had chosen to do so, but instead cancelled it strictly for their own convenience due to the late hour.