As far as I can think the AN2 would be the biggest Single Engine Piston aircraft that you can fly with your licence 12 pax and 1 pilot. The Gippsland Airvan would be the second biggest SEP that you can fly in Europe without a type rating 7 pax and 1 pilot. But the Airvan would be the biggest machine (most pax) on the UK reg that you could fly with your licence.