How to switch from .com to .co.uk domain on an e-commerce platform?

Hello I noticed that we are on the .com version and when searching the boards someone asked how to change to the .co.uk. Someone from shopify said it doesn’t matter because they will look at your address etc… however at the bottom of my account it says 100% of my visitors normally shop in a currency other than british pounds so look at adding them options. I would say that clearly it does look to affect us… So how do we fix this?