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I have used Loctite Body Filler (Halfords) with some success on KT66's, especially the ones that need a complete base replacement such as where the centre spigot on the base is broken off. I have never had one break.

I usually use a junior hacksaw and carefully cut the base in quarters and carefully loosen it from the glass, you can then unsolder the wires keeping them in the correct position for the new base.

Trevor