Thanks for all your comments. Latest departure time is now 2345 this evening, so looking at around a 30 hour delay if that is on schedule.

Tonight's regular BA66 is overbooked so there was no chance of wait listing. I was offered a connection via Baltimore from the gold line but thought It wasn't worth risking a connection to arrive in London 2 hours earlier than the rescheduled flight.
I'm also on an economy redemption, and Baltimore is on a Dreamliner....no thanks in economy!

On the compensation side, they were giving out letters which mentioned a technical fault. So hopefully that will make the claim easier!

And yes, the Clarion is a bit dated, but I can't fault the staff, they've been excellent so far.