Just a quickie, as I've been alerted to a couple more offers to add to the list in last post. Shoot Gardening are offering £5 off their annual subscription until 31st January. The subscription lets you save notes, logs and plans of your garden and plants and interact with other members, among other things.
Victoriana Nursery have a range of discounts from 10-20% available on orders from allotment societies, community projects, smallholders and schools. If you don't qualify for any of those, for a one-off £15 you can join their Scarecrow Club loyalty scheme, and receive 15% on all future purchases, forever.