@feoh This is an awful situation but just to clarify some things
It's not technically required to give the company that much power over your personal iOS devices. They could have asserted much less control and still been secure.
I have worked for a financial institution where I brought my own iOS device. When I was offboarded, they could wipe only apps associated with the company. I had to reinstall my Gmail for personal use and re-login, but was otherwise fine.