Epa
Getting the original EPA done is stage 1. You can download the form from the Public Guardianship Office, but in order to complete it your dad has to know what he is signing for. You could explain it to him as "It is in case you can't manage your own money and we have to do it for you", and if you say this in front of a doctor or similar, this should be okay, if the doctor thinks he understands. Cos actually that is all an Enduring Power of Attorney does, enables someone to manage their money for them. I don't know what a doctor would charge for this, or maybe a solicitor would do as well. No idea what the cost is, but it shouldn't be a lot. I'd expect about £20, unless you had to get the solicitor to come out to do it.
The next stage is registering the EPA. You might not need to do this. Most banks and other institutions will accept seeing the original EPA form, or perhaps a copy, certified by a solicitor (probably costing £7 per copy) even before it is registered. You only need to register the EPA if you need to sell your dad's house, or sell shares in his name, or something quite serious. Then you have to get the POA registered, which unfortunately does cost £120, though you can apply to have this waived if dad has no capital. But it begs the question, if he has no capital, why do you need to register it at all?
One bit of advice. Do not part with the EPA form without taking copies. The Court of Protection lost ours, and despite telling us that they scanned all documents on arrival at the office, they hadn't scanned ours. Fortunately they eventually found the original. Once it is registered do the same - take copies.
Good luck!
Margaret