FOUND IT!!!! It says 'This voucher entitles you to free postage and packing worth £3.50, when you place an order from Issue 157 of The Book People catalogue! Call today to place an order.....0870 607 7740 - Expires 31 May 2007 Quote Ref 157FREE' Both books are in this catalogue, not too sure if it's free if ordered online??!!
Grow Your Own Veg - ref:599-GYN
How To Plan Your Allotment - ref: 599-HPQ
Hope this works ;) If you need any more info let me know and I'll try and help :)