Did G-Wiz even try to build/sell in China. Probably not...

It was an Indian vehicle underneath the UK branding so probably not available in China[1]. Did it fail in the UK due to the Top Gear effect?

The puzzle is that light cars and light vehicles in general have been fairly common and successful in Europe, but get treated as a bit weird in the UK.

[1]http://en.wikipedia.org/wiki/REVAi

I think Top Gear didn't help but the G-Wiz wasn't exactly appealing. Only those (mostly in London) who really saw the advantages bought them. I think some style and marketing may have helped.
Personally I think those who live in and around London are pretty well served with public transport. It's those people with longer commutes in other cities around Britain that need sensible transport solutions, but it's not one size fits all...
Not easy to solve.

There's a lot of journeys that are under 10 miles, carry only one person or occasionally two and involve no more than 4 bags of groceries.  And where you never get above 40mph. The sensible option is a scooter! But I'll admit that it's not great in winter. A microcar would be just as efficient but more comfortable and you wouldn't need special clothes. 

You don't need an SUV for these journeys but if you've already got one, then it works. And maybe that's the issue. If you only have one vehicle (each), it needs to be multi-purpose. Which means that anything else (even a bicycle) is more of a leisure pursuit. 

+Julian Bond You've hit the nail on the head.

I think there's a case for many families having a secondary vehicle type, like a Twizy. I'm certainly considering it.

+Trevor Larkum I've tried to convince my wife to get a Twizzy (with no success). I think they are a hoot and would love to get one. Just a lack of space / powers of persuasion are preventing me ;-)