Here are some links you might find useful:
Horticultural Trades Association - National Garden Gift Vouchers
www.nggv.co.uk
Institute of Horticulture
www.horticulture.org.uk
National Dahlia Society
www.dahlia-nds.co.uk
Royal Horticultural Society
www.rhs.org.uk
Willows Farm
www.willowsfarmvillage.com
CJ Birdfood Ltd
www.birdfood.co.uk
Stonemarket - Quality Garden Landscape Products
www.stonemarket.co.uk