Can't help, but having a similar problem.
iPlayer has worked fine in the past, but for a while (a week or two) we just get a message saying that the server is temporarily unavailable, and to try again.
I've done the factory reset, but it has not made any difference.
The firmware is up to date. The internet content has been refreshed. The network connection is fine, and other network services are all up and running without any problem.
Sony had a lot of problems with iPlayer a year or so ago, I hope they haven't reappeared.
Anyone else having this problem?