@SuzG12
Was this originally set up while in the US? If so, your account, and thus your Channel Store, is identified as a US account wherever you happen to be at the time.
The easiest and quickest way to fix this is to do a Factory reset on the Roku and set it back up from scratch using a UK-based internet connection, and a new Roku account (i.e. linked to a different email address). To be sure it all "took", I'd try to use a UK-based email address, although I don't know for sure if that is necessary.
Factory Reset is found under Settings > System > Advanced system settings
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X