Thank you all, I managed to mangle the first 4 mm of the BB cup, which got rescued by inserting it into my steel On One frame. I’ve also mangled about 6mm of thread in the BB shell, about 1/2 way in so thats going to be a tap only job. When I make a mistake, I do it properly!
I’ve got my spare Shimano BB in there now so it can wait until I give it a strip down before my holiday in August, as it turns out my BB spanner doesn’t fit the MT8000 XT BB cups so need an adapter / new tool for that. Oddly enough it fits my current Shimano (Deore), Token and with adapter Dura Ace BB’s.
As for cost, with 3 bikes, 2 of which could / need threads cleaning, buying a tool to do it, is only about 2x the cost of the LBS, and I’ve got it should I fluf it up again.
Living on a sandstone ridge, means bearings and drive train don’t last long between services / replacement.