Scratchcards in magazines - worth doing?

Titanium

I have done this twice, once I won £20 and next time I won a 6" Digital Frame (I had to pay £5.50 for electric goods delivery though; delivered by DHL). At first I was completely suspicious but my confidence grew after I got these prizes. The point is that if you claim by phone, you won't get much as the prize won't don't make up for the costs.
The company is named National Prize Register, addressed at PO Box 100, Blackburn BB0 1GR. If you google this address, the results include some competitions and promotions affiliated with Sainsburys, 3M, etc so I think it is not a scam, but a clever thing to draw you into calling the premium rate number to claim. If you are lucky you will get a more expensive prize. Now they have sent me another notice, the cheapest prize is a DAB Radio but all I am spending for this is two 1st Class stamps, two Second Class stamps and if I won a non-cash prize, a cheque of £5.50 needs to be sent too.
HTH.