The post-office abuse existed in both the civil and criminal courts. Obviously the criminal side generally had more serious consequences, but I don't think you can chalk this up to the fact it wasn't carried out by the police, particularly in that private criminal prosecution exists in England and is quite common.

[It's also not quite clear to me that the criminal consequences were always worse: being incarcerated for a couple months may not be worse than losing your home and everything you spent a lifetime working to earn...]

In my own experience there is an incredible amount of trust in the system there placed on legal professionals-- but given the rarity of serious consequences for misconduct this degree of trust may be misplaced or at least inadequately supervised.

It's not entirely clear to me how it can be fixed however, because if misconduct is handled seriously then that's an invitation to mire every piece of litigation in an impossible maze of misconduct allegations. To make progress there needs to be an assumption that the parties aren't gaslighting about everything -- which obviously means problems when one of them is!

Injustice hiding behind procedure is by no means unique to the UK however. It happens in the US too.