Originally Posted by Geordie405

Assuming it's all on one ticket then BA will rebook you. BA770 at 7.25 pm has plenty of availability so you should be fine.

In terms of what time to get to the airport, I had a similar situation last week with my flight from LAS to LHR which was also a couple of hours late. It was probably mid-afternoon before BA contacted me (via both e-mail and SMS) to advise that check-in at the airport would remain open later, until one hour before the new expected departure time. So I'd suggest keeping an eye on your e-mail and / or phone for a message.