Sorry it did not work out Andrew.
But still I imagine that the issue is something simple. From what I understand both drivers tested just fine and then when you did the cone surrounds both drivers now no longer read. Given that the continuity between the tinsel wire check out ok my suspicion is that the connecting voicecoil wires have been disturbed. Personally I would, given there is now nothing to lose, remove the dustcap and see if I can lay new wires parallel as far as I could from where the voicecoil wire meets the tinsel 'pip' to the voicecoil itself.
Obviously a new voicecoil and rewire will sort it but that would involve a full recone which probably makes your project uneconomic.
Glad to see your Radfords are now sorted. How do they sound?
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