> When I ask Google Assistant "where am I?" on my phone it tells me I'm in Manchester. Nice.

> When I ask the same question on my Bluetooth headphones it says Liverpool. I can't get it to work. It's been like that for a year. Can't get any support.

Maybe Google's own analytics suggest that very few people in Manchester use Bluetooth gadgets, ergo you are in Liverpool.

Or (more seriously even if as unlikely perhaps) maybe you have a duplicate Bluetooth MAC address, the other one located in Liverpool. Do you have Bluetooth turned on when not using your headphones? Does the answer depend on Bluetooth being on?