The post is good, covering many of the aspects, but if you are trying or just started contracting there is not always a need to make the VAT registration and Limited Company. As I have been freelancing for 4 years as a sole trader.
There are some tax benefits but you have to manage your pay and money very differently as a Ltd, i.e. you have to hold money in the bank enough to cover company bills that you cant spend. Unless you are a high paid contractor all year you are unlikely to make £82,000 VAT base rate.