'Baked' the Big Ben sequence without the UI or 'Bad TV' filters (pre-compose in AE world!) then brought it into a new sequence and re-applied them.
Rendered out a new sequence and all works well. Brought that back into the Remote Control sequence and now wait to see how that looks on FCP.
Will have to adjust the actors reactions to the new length and possibly have a full screen 'hit' of Big Ben for more impact - currently it's seen on a Mac monitor from the Dad and Daughter POV.
Almost there ...