Hello Terry,

There are three main types of heather, plus one more if you're lucky enough to find it: Below are descriptions and some picture links....happy heather hunting:

ling (Calluna vulgaris) aka Scotch heather,
http://www.floralimages.co.uk/pcalluvulga.htm

bell (Erica cinerea),
http://www.floralimages.co.uk/pericaciner.htm

cross-leaved heath (Erica tetralix),
http://www.floralimages.co.uk/pericatetra.htm

Dorset heath (Erica ciliaris) - quite rare,
http://www.english-nature.org.uk/imagelibrary/image_details.cfm?id=111721

More info:
http://www.forestry.gov.uk/forestry/infd-6e3gbf
http://www.users.zetnet.co.uk/heather/wild_heathers.html