Whilst searching for grain free breads, I came across Artisan Breads who make yeast-free wheat-free and gluten-free (although watch out for cross contamination) breads, pizza bases and bread products with quinoa, pea, soya and other non-wheat flours. I can’t try them because the ‘natural leaven’ they use instead of yeast contains maize, but they look good on paper nutritionally.
Here for example is the ingredient list for the Quinoa bread:
Freshly milled (on our own in-house gluten free mill) organic wholegrain quinoa flour (55%), revitalised filtered water, wholegrain demeter rice flour (13%), natural leaven*, sea salt.
They also sell flours to make your own.
Rather usefully, they do a sample box for £4.95, free delivery, so you can try stuff before you commit to filling your freezer up. Have a look.