But isn't this the same as opening your door when served with a search warrant?
Refusing to open your door will result in your door being taken off of its hinges by a dainty set of size 11s. It will result in a fine as the council either board up or replace the door or simply the cost of the door itself. It will result in the officers who deal with you being much more short with you.
It will not result in an automatic prison sentence.
I don't quite understand how you are being forced to incriminate yourself.
Really? Are you actually saying the threat of imprisonment and all that entails isn't a form of coercion?
"I do not recall"
It is a tried and tested legal defence. One this law specifically forbids. It also denies you the right to remain silent, even if that has been significantly weakened in the UK.