It's now better, but still far from being acceptable
It was, indeed, a complete shambles as it was taking about 5 minutes to retrieve each caller's data on the computer. Hence the backlog and huge delays on the phone.
It appears that some parts of the OUH may have anticipated problems because they have carried on running their own appointments systems independently of the patient contact centre. In fact, they are still advising patients to call them directly about appointments and not go through the PCC.
However, it hasn't helped that the PCC has been giving out contact numbers to other hospital areas that don't have anyone to answer the phone (just endless answer-phones where no-one ever calls back). It seems you need to know the special handshake before you can get a contact number for someone who will actually arrange an appointment for you.
And this is after the problems have been "fixed".