David you are quite correct, the Data protection Act 1998 is much abused, not understood, and used as an excuse not to co-operate and often misunderstood, though if you were able to identify yourself on the telephone and authorise the organisation to whom you were speaking to talk to your Father they should have done so, though they may argue they need written consent, which, as you will know, is not correct.
Keep up the pro bono publico work.
Bedknobs, I think you are safe; your husband would have given implied authority, which is what a hospital ward would no doubt argue.