for starters I'd go and see a solicitor - most of them do a free half hour consultation. Choose one who is expert in employment law
if you have household insurance of any description you usually have access to a free legal advice line - though that may not cover employment situations - check your policy
The union rep sounds like a waste of space who doesn't know their rear from their elbow -
Got onto union who said nothing he can do if its their policy although they had never heard of this before but is a private run company so different to nhs run places.
does that whole thing sound like 'I dunno, bee reet' to you?
I hope you get all this sorted out really quickly - and I hope the git who did this gets his comeuppance