After serious thinking Vet Tech wrote :
Question .... is it impossible to undo such connections ie does the
solvent totally fuse the two contact areas together. Does applying
heat make it easier?

I once did that and no, they will not came apart again, however...

You might be able to cut off the cheaper part and using a grinder or
Dremel grind away they surplus plastic from the expensive part.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk