Some of those old Raleighs used 1-3/8" x 26tpi bottom bracket thread, which may be why the OP elected to use the VO threadless cartridge. I doubt that the VO cartridge stripped the BB shell; rather, I suspect that the OP may be seeing aluminum debris from the cartridge plugging the threads. A stiff wire brush or sharp pick may be able to clean them out. If the OP can get the threads clean, Phil does (or did, anyway) offer 1-3/8" x 26tpi lockrings for their cartridge bottom bracket set. Seems like overkill, but if it gets the bike on the road it may be worth it to the OP. Otherwise, if the original cups are in reasonable condition, they can be used with an appropriate square taper spindle to mount a standard cotterless crank.