It seems that the likes of Ali Express and Alibaba are awash with compact, no fly lead RCBOs very similar to what SBS were doing.
The older "tall" RCBOS generally used had fly leads, a blue neutral and cream (functional?) earth. The SBS compacts had neither. Just L&N at the top and L&N at the bottom. Good too that they were non polarised, didn't matter what was in/out. Also they were 6KA rated. They did an unusual 25A rated one which was nice and went up to 40A.
Not sure if you can get these in the UK:
https://www.aliexpress.com/item/1005004798334588.html?