@akmum18 I'll give you a few thoughts and ideas - on the basis you aren't in a position to change to a new employer, so there's no point me giving that option:
I haven’t been given any training or had anyone speak to me about the changes
It's absolutely encumbent on your management to give you and the team training in the new ways of working - You cannot be expected to struggle on like this indefinitely:
I was just expected to know everything, and any time I have attempted to do things ‘the old way’ I am reminded it’s wrong (by new untrained staff).
It's impossible to have a harmonious and supportive workplace when you're all having to guess the right way. You'd be a lot more productive and united, with the proper training. You need to put pressure on them to sort it out.
The team is struggling with stress which is clear from your comment
and spoken to as if I haven’t worked there before which is patronising and hurtful as I was in charge for 2 years so I know the place like the back of my hand
That person is new, you've been there ages, but you all need to work aligned to the new process. If you can get the team together and put in a collective request, it will not only build bridges (solidarity and all that), but it will get you the result quicker (united we stand approach)
'this is my now I’m in charge so you’ll do what I need you to’ with a smile on her face as if butter wouldn’t melt
Without clear direction, and allocated roles/responsibilities, it will be like the Wild West with self-elective Prima Donnas chancing their luck by bossing you about when they don't have the authority. The quicker you can highlight this to management the better.
I don’t feel confident enough to speak to HR or a union as I’m pretty sure it’s only me that hates these changes. If you're in a Union, you pay your subs so they can support you and represent your interests to management. If your job is important, it's in your best interests to seek advice from your Union, they will support you, especially about the above things I've highlighted that management are currently falling way short of their obligations. Your Union could be your best friend in this!