You have to appeal the decision as a whole but then can state within your reasons what you agree with and what you don’t.
There is a small risk that the appeal could also change the outcome of the part you agree with but it’s unlikely as that would mean they’re contradicting themselves.
General rule of thumb is to appeal every time. My appeal was unsuccessful but didn’t change the initial decision.
If I seem a little strange, that's because I am.
Skoda Karoq SEL.