I brew with heather and it turned out great imo. I took 2nd at my local homebrew competition with my heather ale. I did not use any hops.
It is definately a different taste than hopped beers. Hard to describe. More tea like? Herbal for sure. As to where to get heather most homebrew shops (especially the ones online) carry it dried. I have taken to growing my own (along with hops) cheaper and fresher that way as you have now idea how long the store bought has been sitting especially since it is not a high demand product it would seem.
I have brewed my recipe about 3 times and have played with the amounts. First time I brewed it was the winning batch but I like to tweak. I have mostly done 1 gallon batches until I am satisfied. Amounts have been around 25 g for a one gallon batch at various times. In the mash, in the boil, at flameout. I would not recomend dry "hopping" as they do not have the same acidic nature as hops and I had my one 5 gallon batch go sour dry hopping. An unintentional lambic shall we say, not undrinkable but not what I was looking for. Pineapple lambic...
Anyway. It is an enjoyable brew as you know. Give it a whirl.