I did this yesterday and used the free £20 bet for this upcoming Candian GP..
I am not a betting man but this seemed too good an offer to miss.
Sign up with Paddy Power today, making sure your first bet is a £10 wager, and you'll get a FREE 6 issue subscription to F1 Racing magazine. If that wasn't enough you'll also get a FREE £20 credit for you to bet on anything you like at PaddyPower.com
PS. After signing up and placing your first £10 bet, you'll receive a confirmation email from Paddy Power within 24 hours, you'll then receive a written confirmation (to the address left on your Paddy Power account) from F1 Racing magazine within 7 days and you are ready to enjoy your subscription.