We have the same issue in Germany. :( Car drivers just get away with absolutely everything unfortunately.
It’s not the rule.
So what happens is this, someone says you’re allowed to park on the pavement as long as you don’t obstruct the road, then someone else says no and quotes the highway code. Then you point out that the only thing you’re not allowed to do is park on the payment in London, and elsewhere you should basically not do it if you can avoid it.
No one is going to get arrested for parking partially on the pavement outside of London unless you’ve been a complete dick about it, or if it’s unnecessary. For where it’s necessary as long as there’s no other parking restrictions then you should be fine as long as pedestrians can get past.
The highway code is fine in principle, but the people who wrote it have never been further north than Bedford.