Policy disagreements, sure. And you can certainly read those as questions of honour/morality. Robin Cook over the Iraq war, perhaps, or Michael Heseltine over the Westland affair.
As for 'resignations' on the grounds of ministerial misbehaviour, I'm afraid they almost always come down to one of two things. Either the PM isn't personally prepared to put up with it (in which case a resignation is requested) or the political fallout has become so severe that either the minister doesn't want to face the music any more (in which case they will resign more or less in disgrace) or the PM can't afford the political cost of extending cover any further (in which case they will be asked to resign more or less in disgrace).
I am quite sure there are honourable people in politics. Estelle Morris famously resigned as Secretary of State for Education on the basis that she didn't feel up to it. There are probably a handful of others. But resigning without being forced on the grounds of a self-identified moral lapse is astonishingly rare.
Again, you occasionally get people resigning on the basis they think their PM is dishonourable, but even then it's mainly just politics. (Everyone currently leaving Johnson's cabinet knew of his objectionable character before signing on, for example).
The modern Conservative party mostly has a reputation for corruption (which we politely call 'sleaze') rather than honour and probity. That dates back to at least the early 90s and has been recently reinforced. Labour's reputation is in the gutter too, though possibly not to quite the same extent.
(I teach political communication in a British university and have previously interned in Parliament, FWIW. The strong tension between our 'good chaps' theory of government (with its actors behaving honourably at all times) and the nakedly political behaviour of ministers and parliamentarians in actual practice has been part of what we teach politics students for decades).
