I would say his boss would need to give more than 24 hours notice for a change in shift pattern, unless his contract says otherwise.
Even so, the notice period does seem unreasonable.
That's right, if they demand notice, then it should work both ways.
I don't get paid overtime, so if I really don't want to do it, I don't. f**k them I say, there's no promotion looming so they can shove it.