I've always used front brake on the left, even when I still lived in the UK. Most brake calipers are designed for front-left, as the cable will then curve more easily to the right hand side of the fork (front-right brake cable routing looks pretty weird, especially on smaller frames). I think the vast majority of frames nowadays have the rear brake cable routing to the left side of the TT too - designed for rear-right brake setup, where the cable curve will be much smoother.
BITD, when all bikes had downtube shifters, front-left also meant that braking (with your left hand) while changing gear (with the right, both front and rear mechs) was possible. Maybe not too necessary when just out riding, but pretty useful when racing.
And FWIW, I also ride a motorbike. It's a scooter with no clutch, and has the rear brake on the left, front on the right. I have never had trouble at all swapping between the two or getting my brakes mixed up...
So although I think bikes and brakes are designed the way they are because a front-left/rear-right combination is the most common, there's nothing wrong with having them the other way around.