Hi,
RE-Ridden left-hand side and right-hand side gear changes and I much prefer the right-foot gear-change, to me a right-handle bar mounted front brake & left-foot rear brake, is when riding  a much more balanced proposition , it feels "RIGHT". Yes, we do drive on the Left and  this probably had something to do with the lay-out initially too,  as presumably the people, who designed Veteran & Vintage machines actually rode-them on the road, the final development would have been a trade-off between practicality and comfort.
Alas, the US of A, probably as a Trade Barrier,  out-lawed right-hand gear change mechanisms on Imported bikes in or around 1975 & of course the US of A was an important export market.  I would  by preference,  not consider purchasing a Left-hand change British bike, its not authentic, its not what I prefer as a riding- control mechanism, neither would I prefer the Decimalisation, the Metric system, ( ever wondered why the mathematical ability of the population has plummeted),  or the EU. 
Cheers
JBW