BA Amex PP offers £750 after a 4 hour delay and a further £1000 after a 48 hour delay (all sectors but last inbound). Amex Platinum (Charge card) offer £300 per person after 4 hours delay and a further £300 per person after 48 hours. These sums are in addition to any compensation from the carrier (which depends upon the class of travel). I got $350 I think (after some argument) when BA lost my baggage on route to SFO in F. I also had a nice little shopping trip at the Forum Shops at Ceasars in Las Vegas at Amex's expense.

Having checked the T&C's prior to my domestic flight this evening it seems that domestic flights are covered as well as international ones.