Well if he’s over here at the time there is the May Day run, well on May Day.
Starts at Locks Bottom, just off the A21 near Orpington, and goes to Hastings. It can easily be done on a scooter as I’ve passed “runners” on Honda C90’s.
It’s a great almost spontaneous affair with a huge cross section of the PTW community.
I recommend Modern Vespa as a good forum, especially for more modern Vespas. It is a US forum, but there are plenty of UK and European activists on there who refer to themselves as the Donkei SköK SC. DSSC do organise rides in London and SE.