I don't think you will have too much of problem finding enough charging points. If you look on Zap-Map there appear to be a good number. Some EV car dealers may let you charge for free, there are several who will in the city of Norwich, where I live. It would be best to do research and check availability of places before you take the plunge.
With regard to parking in residents bays, you could get a lockable cover from these people http://www.specialisedcovers.com/car-covers They make one which completely covers the Twizy and although a dermined thief could obviously remove it in time, it would stop anyone but the most determined from tampering with your car.
They do a long term outdoor storage cover from £299 called "Stormshield" and you can order onewith your car's number plates on it, (an extra cost option) so it is legal to park at the kerbside. They would also provide one with a clear pocket to display your residents parking permit.
I would buy a Twizy with just doors and then find the best windows for your needs, afterwards, reading all the reviews of windows, on here first, is a good place to start. You may even decide to do without them!
Good luck buying a Twizy, I am looking for one myself at the moment. I hope some of this helps you.