The wiring moves into a big bundle and heads in the direction of the dash. So potentially right. I'll pull the head unit and check tomorrow. Still have another one in the arm rest, one in the glove box and one in the phone harness so thinking there must be a hub somewhere

The armrest and glovebox USB have nothing to do with each other. They are not connected in any way. The glovebox usb hooks to the CIC. The armrest usb hooks to MULF or Combox in the hatch. This is for North American BMW so I may be wrong for other markets.

I'll try and verify that, my logic had been that I had lost both so assumes something in the path (hub) being a common component

Trust me, unless a lot of water came into your car in the front and wet the hub, I truly don't think it is, that's what I thought as well and with my big hands found the hub, replaced it with a brand new hub to find out that it wasn't that. It turned out to be the mulf2...

Buy a used one on eBay from a good seller or find someone who has the same car that will let you connect theirs to check or go to your local junk yard and pull on and test it out before you spend so much time looking for the hub...

Because for some reason, from what I've read, the location was different depending on the set up...

However, did I listen to the advice that I just gave you? Nope....lol I still did it anyway just to see...lol

Have fun

Can't fault your logic, will pull the MULF2 module and see if its blown the port