When it comes to radical my vote could never go to a spring piston gun, whether the piston flies forwards, backwards or upwards, as a design concept it's been around since the late 19th century.
I would say there are two contenders, first is the Brocock (Saxby Palmer) air cartridge system. This enabled airgunners to experience proper, firearm quality guns with proper firearm mechanisms.
The second is at the oposite end of the quality spectrum and it's the Umarex PPK copy. Not only does this pistol have firearm looks, it also strips down quite similarly to the real thing and gives a close aproximation to the feel of firing the original gun. The Tanfoglio Witness is even better in all those respects, but I believe the PPK planted the seed.
The South of England has 2 good things, the M1 and the A1. Both will take you to Yorkshire.