Started my Vespa 125 U from 1953 today, last driven in October last year. Had to use starter gas as todays petrol deteriorate rapidly. Before that I had to change the inner tube of the rear wheel.
It's a big difference driving the U compared to the Lambretta TV 175. Obviously there is 125 cc against 175 cc, 4 hp against 8,6 hp. And the riding position, you are very close to the handlebar.
Sitting on the pillion seat doesn't make sense - you only look silly!