Hi all. For anyone else interested in this topic I tried the solution kindly supplied above here are the results:
I created a new account using a different email address from the previous one I used. I used this english language link: www.ig.com/ie
I selected Sweden as my country of residence, and the Web interface is now in English. Yay!
I unistalled the android app and reinstalled. Probably don't need to do this but it did it just in case. Then I logged in using the email address I used to create the new account. App is in English. Yay again!
One thing to note is that the second account still held the same balance as my previous one. So it isn't a completely reset account. Rather, it's just that the language has changed.
The only minor annoyance now, and difference I have noticed so far, is that previously my currency displayed as Swedish kronor which is what i in fact wanted. It now shows as Euros.
So apart from that, thanks to IG for the help and working solution. If there is a away to switch back to Swedish Kronor without changing the language, please let me know 😀