After much umming and arring finally bit the bullet, threw caution to the wind and took a blow torch to my beloved Nemesis clone.
Gave it a good polish first using micro-mesh up to 12000 grit. Then knock up a jig out of threaded bar and a couple of sockets to hold the tubes and placed bar in a cordless drill. Set drill to a slow speed and fired up the blow torch.
Very pleased with the results
Sent by carrier pigeon from the edge of a babble abyss