Opcom mate. Ebay, there copy's but they show you everything. When I get home I'll link you to a trusted seller, he's a trader on a few Vx forums. Its uploaded onto your laptop and you plug the lappy into your car.
You can also reset and read engine codes with a free android app called Torque but you also need the Bluetooth interface, they cast about £13, search you tube for torque app vids.