I like these
usb-nachruesten.de for simple bluetooth and hands-free addons, although last I checked they weren't shipping to the UK any more. Simple and reliable if you can get hold of one though - that's what I put in Paul's FE.
There are of course the OEM-lookalike Android units that Marcel and I have too. They have Carplay for a higher level of integration, but are obviously more complex to fit and not really plug & play.
Weird faults like that in the TCU are usually a symptom of water ingress. Alas the TCUs are becoming pretty unreliable these days and so they are quite rare and expensive. I'd swap it out for a known-good unit to see what happens before chasing wiring issues. I may have one I can lend you for diagnosis - I'll have a look.