I sat in a Twizy at Bromley Pageant of Motoring, and while I quite like the styling and concept, the child's back "seat" is really only suitable for shopping, very claustrophobic. As a fun car for occasional use possibly alright, but the clear side screens have large gaps, like around the wing mirror area, so it is NOT weatherproof like a normal car. In Winter or rain you would have to dress for outdoors, as on a scooter. For me this does limit its usefulness. I cycle in virtually all weather except icy road conditions and the exercise keeps me tolerably warm. However the Twizy looks like a car more than a scooter and you are not pedaling as on a bike and I feel that in UK you would soon get bored of being wet and/or cold. At Bromley they were not providing clear information of battery price, range, life expectancy etc., but I understand that dealers do provide this and it is a reasonable package.
I would be interested to learn how it compares with GWizz, which I know about from Bob's detailed information here, and from what I know so far I would be inclined to choose a G Wizz over a Twizy. Squeak and I could go for a drive, or to the shops without the risk of either of us getting soaked in a G Wizz!