Thanks for the response, Stuart. It sounds like I've totally
over-engineered it from the description of your retaining wall
I think so. As it isn't very high, and isn't going to take any weight, the
only thing you have to think about is the soil. Ours is pretty sandy, but a
clay soil can exert a lot of pressure when it freezes.
I left a gap here and there in the mortar on the bottom course for drainage.
I wish I'd left a few more to grow trailing plants from. Lavender's pretty
good for hiding the brickwork.