Hello there!
I will try to share a bit of information that i know.
With regards to your driver's licence you are allowed to use it in the UK for only 1 year. After that you will need to apply for the proper UK Driving Licence which you have to take the written test and pass it specially the practical for a period of time and you can search on the internet to get a cheaper rate an hour.
About the dangerous place in London..there is no such place as safe! Everywhere is dangerous you just need to be very careful.
Theres lots of posh places round central..
Renting a bed flat is very expensive specially if you chose to live the city. Even a room to let maybe you can find no less than £500. So try to live outside London and work out your train or bus fares as they can be cheaper for you. The more you live in the city is the more expensive!
Before you start work, you will have to register yourself with the National Insurance for taxes! YOur employer will get you your CRB (Police check) and will have to wait when it releases before they will tell you when to start your job.