The sealed cartridge bearings on Viscount BBs can easily be replaced. They're press fit, so you need to remove the circlips on both sides of the spindle and knock out the spindle with the frame in a vise and a block of hardwood to protect the spindle end. Give it some good whacks with a BFH, and one side will either come out with the spindle or once the spindle is out, you can knock out those BBs with a long punch or rod. You can find replacement bearings for around $5 each. Those spindles were also prone to failure at the circlip grooves, but those are much harder to find replacements for, unfortunately. And you're out of luck to install a standard threaded BB as you have no threads on the shell.

Neal