If you know someone else who can do it, that's fine. Just have it done and let the Estate Agents have a copy. Check the prices, and make sure if you arrange it yourself that it's a proper one by someone qualified to do it.
Be careful who you choose I got a person recommended by estate agent whos charges were £55.00 she didnt do it right she said she would ammend it and I didnt hear from her again I then got another person to do a epc for me for £35.00 and he was excellent