Hi Hammerman,
The other thing you could consider doing is reporting this meglomaniac to CSCI, the regulatory body for care homes accross the UK. Try :
http://www.csci.org.uk/complain/share_concerns _and_complaints.aspx
I agree with everyone else's posts on here about taking advice from a solicitor, and your wife has no legal necessity to hand the uniform back to the manager; she can simply return the clothing to the receptionist or a member of staff on the premises. Remember your wife is no longer employed by this woman so she doesn't have to stand there and feel obliged to take verbal abuse from this person. She can just hand in the uniform and walk straight out.
Then, seriously, you need to go to Citizen's Advice and claim for your wife's witheld pay. It's relatively straightforward.
Good luck against the dragon!!!!!!!