No. He’s not sorry it happened, just that they’ve been caught out. He’s misled Parliament and that’s a resignation offence - even if it wasn’t, I think eventually there will be no way out for him. He claims he didn’t know there were parties going on, and was under the impression that the ones he attended were ‘staff meetings.’ As PM he should have ensured that he and his staff were adhering to the rules which applied to everyone else at the time. He didn’t, and ignorance is no excuse.
According to the news this morning there’s more evidence to come to light, and I don’t think it will take more than one more revelation to make his position impossible. He needs to jump before he’s pushed.