You get a voucher with the phone which you have to send back with 2 forms of ID. Sent mine back recorded delivery and got the PS3 a week later.
I know technically it's not free as your paying £30 for 18 months..... but I had my old sony W810i for 2 years on a 1 year £30 a month contract. So I got a new phone and a free PS3 for the same as I was paying before.Plus I get more texts and mins than old contract.
All the big phone shops have all sorts of crazy free gift deals at the mo.... free sat nav's,laptops,PS3,360 wii etc