When I submitted this post I was looking at the pictures for ages thinking something didn't add up!
RE: TF vs Brick, I was thinking that the deciding factor would probably be reduce time to build, resulting in reduced finance costs (less time with high rate self build mortgage).
What I'm struggling to figure out here is if I've got £300k to build this to completion, how much "wiggle room" do I have to play with for some creature comforts (to me anyway) things like PVs, AC, GSHPs etc. Or, perhaps it would better to just put those niceties out of mind for now?