Bank refusing joint account info to PR.

A_B_C

My brother died intestate and its me that's the closest living relative. When I asked his bank for IHT values of his accounts including a joint bank account held with his unmarried partner,
they refused siting DPA. I pursued this and was eventually told the joint account was no longer in his name and would need probate (sic) for the bank to do anything.
What are my options - its obvious that statutory rights under Inheritance Tax Act 1984) are being oppressed so what are remedies?

Keep_pedalling

As the joint account does not form part of his inheritable estate its value is only really important if his total assets, including half the joint account, exceed £325k taking his estate into IHT territory, is this likely to be the case?

Have they released the money in his other accounts to you or are they refusing until you obtain probate?