I would have thought they would have closed your account but perhaps moved it to a new account if the original had been compromised.
Did they explain which criterion/criteria you no longer met? Have you asked them?
You'd need to write a formal complaint letter before you go to the ombudsman but you also need to think about what you want- do you want a Barclays account, do you want an apology, do you want compensation...?
Have you tried opening an account elsewhere?