50cc has to be the most dangerous sized engine, it's just too underpowered to keep up in city and urban traffic, let alone out of town.
I often see small bike/mopeds/scooters pootling along at 30Mph, huddling the curb-line to keep out of the way, this leaves the rider open to danger from impatient drivers who pass very closely.
If anything, I personally feel that 125cc should be the minimum, with of course a mandatory CBT in place.
The motorcycling demographic is older, but there are still lots of 125 riders on the roads, the problem from there forward is the immense cost of gaining a full license, this is what inhibits the 125 riders progression.
Perhaps @G robbo you should contact MAG (the Motorcycle Action Group).