I called the Intermediary help line for a client only for the client to fail her security checks, she got mixed up with her N.I.N.O. and post code, I asked to speak to the supervisor and again got the old story data protection, did I mention that the client was 72 years old lady deaf and partially sighted and had just cremated her husband 3 weeks previously in a bit of a state ‘who cares’.

I tried to explain this but they had overheard me prompting the client by saying ‘ITS YOUR POSTCODE’ they are asking not do you have a ‘PAST CODE’ French comedy springs to mind.

Needless to say I hung up in disgust.

People who work in any kind of call centre tend to be automatons. It's the nature of the job.
Try hanging up and calling back straight away. You'll probably get somebody different, who might be more co-operative. And brief your client on what to say before you phone back again!
You could also try explaining the client's situation to the operator before you hand the phone over, especially that it is some-one hard of hearing so they will have to speak more clearly and slowly. Sometimes this works. However, it might not. I have once explained to a tax credit person on the phone that she would have to speak slowly and clearly for the benefit of my client, who is Polish. Said operator then rattled away in a thick Geordie accent, which simply resulted in my client frowning and shrugging and handing me the phone back again. The operator refused to arrange for a telephone interpreter, and refused to use my own interpreter, so I had to send a written complaint. I shouldn't have had to.