You have to remember that with LHR, BA are not remotely interested in point to point traffic, they only want traffic to feed into their long haul network.
BA could start up many UK domestics but how much of them are going to yield a decent number of connecting pax?
I'll be very surprised to see any more UK domestic from BA and I'll also be surprised if this LBA route survives for anything over 18 months on this schedule.