My mate just bought a Sony Smart Tv off his brother and wants me to go around and help him sort it so what I want to know does the TV need a USB adaptor to connect it to the internet or is it dependant on the model number whether you need one or not??
If I need one is there a cheap USB adaptor or is it A Sony one only??

Depends on the exact model, the latest models have a built in b/g/n standard Wireless Cards and indeed a wired Network Card.

Older models may require a Sony specific USB dongle, any old cheap one is unlikely to work.

It's dependent on the model - on some it's built-in - if not you need the proper Sony one,

However, why not just plug an Ethernet cable in to it, or use homeplugs. Likewise you could use an external Ethernet/Wireless adaptor, such as the Edimax EW-7228APN to provide Wireless for it, and for many other uses as well.

If the TV isn't wireless enabled this is another alternative to Homeplugs or ethernet connection which is fairly cheap easy to install and works well
http://www.amazon.co.uk/Vonets-VAP11...2319422&sr=8-1