Rather than spend lots of money on ordering a letter from Santa for your child, the Royal Mail can apparently help you out with this for the price of a stamp.
Ask your child to write a letter to Father Christmas and send it to Royal Mail's special address by last collection on Wednesday 15 December '10. Santa will reply by Christmas Eve, apparently. You need to include your child's name, a return address, whether they are a boy or girl, whether they have been good, and what they would like for Christmas.
Send it with a 1st or 2nd class stamp to:
Santa,
Santa's Grotto,
Reindeerland,
SAN TA1
They'll be sent a pretty little card with a standard greeting poem, plus a 'put the clothes on Santa' cut-out game.