Well, for whatever reason the system thinks you are in Romania (I think that is what RO stands for). Are you by chance using some VPN for your internet or your browser (TOR)? Or something else that could explain this?
I'm kinda hazy on the exact details for the reason for this question, basically some EU online commerce regulations require 2 indicators for the country of residence, and Dominion Online asks the user and compares with the IP. Both methods can give errors, in this case the IP geolocation *seems* to be incorrect (Romania and UK are not 'near' each other).
The slightly unsatisfactory solution to this would be to put in Romania as your contry of residence, and then see how much VAT is added.
If you wait for 2 month, UK might no longer fall under that regulation anyway...