.
...lastly, there are many UK posters who have previously stated on this forum that they simply ran a set of standard threading taps through a Raleigh threaded BB shell, and installed a standard threaded sealed unit bottom bracket cartridge. They report good results. I think this works because even though the new threads you cut doing this are not perfect, a sealed unit BB has its bearings and races internal. So there's not nearly as much force applied to the BB shell threads as you would have in a cup and cone, loose ball assembly. The shell threads only serve to position your bearing assembly in place. Indeed, the things that position the unit are often made from plastic (sometimes aluminum), because of this.

But all this presumes you have Raleigh threading, which you might not. You need to check that out first...you can use a standard threaded RH threaded cup as a tool, to check the threading on the non drive side of your shell.