I'm not sure you are too restricted in your choices :-) Of course, some heaths/heathers do not attain the height you are looking for and some can spread much wider than 1-2' but overall, a great many will fit into your size requirements very nicely. And it is also recommended that these plants be sheared back at least once a year to remove old flower stems and to keep the plants tidy and compact - that can help you to keep size in check as well.

Winter blooming heathers (Erica species) can add a lot of interest and color to the garden in winter so they might be a nice choice. However, the largest range of sizes seems to be centered with the Ericas, all the way from rather flat groundcover types to tree forms, but many will fit into your size limits so it's a matter of seeing what's out there and what works for you. I'd think the best place to start would be at your local garden center and take it from there! Planting can be done at any time the plants are available and the ground is workable (neither frozen or excessively wet).

Just a couple of names to get you started. You could consider Eric x darlyensis 'Kramer's Rote (one of the most popular varieties we sell) or Calluna vulgaris 'Tib' (RHS Award of Garden Merit). Both are excellent choices.

Thanks gardengal, much appreciated. I forgot to say that the area isn't full sun - it's by no means deep shade either - but will heathers generally be forgiving of not having full sun all day?