I think you have answered this question yourself.
I spotted what might have been Number 1 treating the South East of England as the base leg
If you are not sure of the location of circuit traffic, then always assume the worst. Carry on downwind until either your contact turns base whilst you grumble under your breath about ocean liner circuits
or until number 1 makes a position report to identify their position and make your decision accordingly.
A few extra minutes in the circuit won't kill you....
Just my opinion..