Sounds like a problem with the navigation equipment if he was flying over Buckinghamshire en-route from BHX to EWR
It departed from 33 and turned S on what might have been a COWLI or CPT SID. Whether it was heading towards Bristol Channel and track similar to that now being followed by UAL16 or was being vectored while crew analysed a problem I don't know.
Now found local press report referring to an unspecified 'technical issue'. While not making connection report also mentions extreme weather being forecast for eastern US.