I'm assuming you're in the UK so these exact sites might not work, but I'm sure you can twist it to fit your needs.
I went and visited the sites of popular places to buy/rent video games here in the US (Gamestop, Gamefly, etc.). Most businesses have a link in the footer of their website to their affiliate program. Click that, sign up, and place the offers. Your audience gets fed offers from large companies that they're probably already aware of and have some level of trust towards.