[Arran]

I think part of the problem may be in soldering to the stubs of the original loctal tube pins, I can't remember the exact alloy but it was not copper. The connections inside the tube were spot welded to it, that isn't to say that you can't get solder to stick to it but it may need more heat, or a different flux. However you could make an adapter plug using stiff copper wire of the appropriate gauge, but it's a lot of work. I have no experience with tube sockets from the "middle kingdom" the last tube sockets I bought were some international octal ones from Ukraine, and they were Soviet/Russian copies of Amphenol top mounted sockets, that were well made.
Regards
Arran