In the first place, would be asking PX either through the ebay contact seller, or just giving them a call. You may need to take it to a LBS to have the threads chased, but would be looking for a specialist one, as Italian thread cutting tool is very specialist, rather than a BSA/English which most shops should have.

Going by this https://www.planetx.co.uk/i/q/FRSABC...luminium-frame which looks to be a very similar frame, the BB is Italian thread