Proper Trigger's Broom now, this. Not one component left from the original build. I was actually looking at the Casserole before I got there Soma, but I got a bike fit and my size was sold out. One of the shifter bosses fell off the Soma at the start of lockdown, then I spotted this on Ebay, fairly straight forward swap and the geo is very similar.
Need to finish the cabling, get a 30.0 seat clamp, and possibly nicer a seat post.