The problem, as I understand it, is that the Updates app is trying to update Start and can't. The solution should be to get rid of Start, which ought to have uninstalled itself a long time ago. As you're only posting now, I wonder whether the phone has been unused for some time and that process has simply been lost in the mists of time. The S5 is quite old now, so I'd assume that, as long as it was kept updated, it's probably got as far as it can.
The obvious solution would be to turn off notifications in the Update app, but I don't know whether that's possible. Recent versions of Android exercise a lot more control over how apps behave and there's quite a lot you can do pre-emptively that wasn't previously possible. Can you disable the Updates app at all? (AFAIK, if only works on Vodafone apps and probably isn't critical). If none of this is possible, I fear there isn't much more you can do.
What version of Android is it running? I'm finding that more and more apps need Android 7 and above, so it's possible it's coming to the end of its useful ife anyway.
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