Go to the normal log in page at http://www.paypal.co.uk
and on the right hand side there is a little box stating that you could win cash if you register your mobile phone to Paypal.
You simply enter your mobile number, and a pin. They call you and ask you to enter your pin to show that you are the mobile phone owner, then you can continue to a pic of a mobile phone - click on the screen to see if you are an instant winner!!
thanks to dawnylou on another site where a few people have won £5