I've no idea if related, but a couple of evenings ago there was a formation of 5 or 6 jets flew west to east over where I live (to the north of me across the midlands), all were leaving contrails, so definitely in formation at high level, I went to check Flightradar24 to see if they showed, and they didn't show.
If RAF/USAF they normally show their transponder over the UK, these were not displaying it, and they wouldn't be in UK airspace without permission, and somebody knowing where they were, otherwise it would compromise normal aviation.