Normally in America you don't have to pay a fee (long distance call or otherwise) to win a prize. But haircut might be right, calling the number isn't 100% necissary, but if you want to find out your prize, you gotta call. (It would drive me nuts anyway). Is 5 pounds alot? From the last conversion I remember, that is about $12 American, but this is just a guess-timate.
Erp, I just read the 'rules' and it says (referring to the "call"):

(sorry about the big size of the image, I wanted it to be readable)
So you CAN send a snail mail to get the "personal code" but it wouldn't be enough time for this sitution. It would only work if I had found this at the beginning of the month. (Next time I get this Magazine, I'll keep an eye on the date and maybe we can catch it in time.) If someone really wanted to, they could use these rules to get both a game card AND a claim code for the next contest (which seems to be monthly).
<B><i><FONT FACE="Tahoma" SIZE=2 COLOR="white"I was dead before I met you, I was born the day you loved me, and my love for you will keep me alive forever"</i></b></FONT>