The BBC, in their wisdom, decree that Iplayer is only available to UK IP addresses so that only license payers can watch it. I pay the BBC a license fee therefore I'm entitled to watch what is on Iplayer.
gg,
You will find the BBC don't "decree". The BBC are almost certainly only merely fulfilling their contractual obligations with the production companies whereby the content is licensed to be broadcast to UK resident license payers. The broadcast of a commissioned programme abroad will likely fall under separate contractual conditions and associated commercial terms.
In order to prevent a breach of contract, the BBC are likely merely taking all reasonable steps avoid such a breach.