if thats not a sackable offense, it should be.
He probably was sacked in the end.
those documents had nothing that could benefit Poland.
Even if they did, he'd probably have been handed over anyway - there have been a few cases like that round the world, and Britain and Poland are friendly countries.
If they didn't, he'd have been on an EAW anyway, so he'd have been extradited automatically, and that would be on the system at any airport should he enter or leave Schengen.