It's sorted. The "press 4 and 6" instruction was a bit misleading, you then have to scroll across, and press continue, this then gets you into a network set up page, which is different from the usual view you would have when first setting up (with a very annoying password input method!). This then performed a system update, which solved my other problem (not being able to access "my products" and add Paramount Plus - all sorted now)
