I want to fit a towbar to my A3 1.6 Diesel sportback as cheaply as possible.

I just want to tow a small box trailer and do not need systems that will work with brakes on caravans etc as I will have to remove it in a couple of years when I give back the car to my employer. I just want to buy a cheap towbar kit from the internet and get someone to fit it.
I have spoken to someone who can do this but they have suggested that I go online to this forum to ask for advice on where to find the plug to connect to(to avoid removing panel uneccessarily) and to ask for any tips from someone who has already done it as he thinks the car monitors wire resistance etc so it is not as easy as it used to be.

Can anyone help?