Not long now.
The unknown plane from this morning was 2-RBTS, I've managed to identify it as it entered UK airspace and from checking it's flight history. It flew from Witchita, KS via Gander and Keflavik to the UK.
That was going to bug me unless I nailed it down. Nice.
Update on 2-RBTS. Seems to be headed for the Channel Islands.