Here is the main page for details of the prize, you have to order :


http://www.grattan.co.uk/Web/main/welcome_promo.asp

but if you want to enter via the plain paper npn route click on this link 
for the full address details:
http://www.grattan.co.uk/Web/main/welcome_terms.asp

send details to address mentioned in 2) of the terms and conditions.