Under Custom Clean I can opt out of clearing log in names and passwords, but if I use Health Check it removes them. Is there any way to avoid this please?
No there isn't.
Health Check uses it's own cleaning rules, you can't change those rules.
As you already know Custom Clean can be modified so as to leave things alone, or add things that you want to clean.
If Health Check could be modified in the same way that Custom Clean can be then there would be no point to having both.
You can change which one CCleaner shows you when it starts by going to Options>Settings and changing the 'CCleaner Home Screen'.
Thank you for your prompt and helpful reply. I have now changed the settings. Many thanks.
Just to add that Health Check should not be cleaning any logins/passwords that you have saved to your browser. (Custom Clean can clear those if you tick the box).
But it will always log you out of sites by clearing the cookies for that site.
Custom Clean will also log you out of sites by clearing their cookies unless you have told it to 'Keep' (not to clear) those particular cookies.
See Option 2 here for how to 'Keep' cookies:
https://www.ccleaner.com/docs/ccleaner/ccleaner-settings/choosing-which-cookies-to-keep
TBH I always let CCleaner clear the cookies and log me out of sites, it only takes seconds to log back in again next time.