Mac keyboard language changes to US when opening an image in Photoshop

I want to use the GB keyboard on my mac, and this one only, so not use the US one, as I want my hashtags and Pound signs to be in the correct place. 

In Mac keyboard settings, I have deleted US as an import source, whoich then completely removes the US keyboard. Things work fine, until I open an image in photoshop, then the US keyboard returns, and is then the default across the system, which is incredibly frustrating. For some reason, opening Photoshop restores the previously deleted keyboard. I know it is Photoshop doing this, and I can physically see the US keyboard reappear in the top menu bar as Photoshop opens. 

In Photoshop settings, I can only see one place to adjust language, in Interface. Here there is the option to change UI language, however International English is the only option available. 

Any suggestions to stop Photoshop interfering with my Mac system settings?

Thanks.