Don't be seduced by the cheapness of Chinese scooters. It's really hit and miss with them Having said that a Colleague at work has been using a "Baotian" for a couple of years and has not had any trouble with it. It's a clone of a Vespa even down to loads of Italian flag stripes.
Firstly - check the licence very carefully. The old "Group E" that used to allow you to ride a 50cc on a car licence hasn't applied for quite some time. If in doubt, give your local bike school a call, or DVLA - they can be very helpful. Remember, if you aren't complying with the licence law you're not insured... Secondly - I don't know about Chinese scooters, maybe they are cheap enough to be seen as "disposable transport", but Sym scooters are excellent. I didn't believe scooters could be so much fun until I had one of these... And Sym were set up by Honda so they know about build quality. After several years of abuse, mine still works fine...
Ive had a habana retro 125 jobbie ( not the one with the harley bars) for 12 years now and its been great. They do a 50cc version as well, although I had to add a topbox as you cant get helmets under the seat.