I had to scrabble around to find this page - they don't make it easy! Hard to beat 5 months of Gardeners' World for £5 delivered - not seen the 3 for £1 offer for a couple of years now so this is the best you'll get. Hit & miss with TCB so all I can say is good luck & do tell if you get it tracked. UPDATE: MINE HAS TRACKED!
Other decent magazines with similar promotional price, such as:
Homes & Antiques
& various others
To get this deal you'll need to set up a DD, which don't forget to cancel once they have taken your £5 unless you intend to continue with the subscription.