Latest version of OEM release for Windows 10 is 1803 build 17134.48.
You have what appears to be a Fast Ring Insider build -- 10.0.17134 Build 17134. You've not moved to version 1803?
Screenshot of UAC warning would help here. (In any case, merely running in a Standard User account will help mitigate your issue as you would need an administrative user password to make system changes.)
Windows update hasn't offered me an update, so I haven't updated.
I appreciate the advice, but seeing as I often install and uninstall software I'm happy being on the administrator account. I've never has any issues before and it seems weird to have to change the whole way I use the computer just because of some weird thing happening with Avast which I assume is an error?
I've attached a screenshot in case that somehow helps.
Paul