Swapping between AppleIDs to update apps

I have created 2 appleIDs, one for France and one for the UK. I was told this was the simplest way of keeping apps in different regions updated rather than have to cancel Apple Music etc each time. I need to upgrade a UK app so initially I logged out of App Store with my French ID and logged back in with my UK one. I went into the app, clicked upgrade (because it told me it needed upgrading) and it said I could'nt upgrade the app because it had been 'purchased' with another appleID (its a free app). When I tried it again, it said the developer had deleted the app (which isnt true!!). Does this mean I cant upgrade without having to cancel everything? Another thread said that you could change AppleIDs simply by going to Media and Purchases, clicking through, clicking the avatar and changing appledID there .... but I only have "Sign Out", Password Setting and View Account not anything else. HELP!! I really need to upgrade this app