Sometimes the issue is a simple one.
The name on the bank account has to exactly match the name used when you register on Ebay.
So, if the bank account name is James G. Smith but the account name is Jim Smith, then that would not be accepted.
Get your friend to check that the names are an exact match.
Then. if there are still issues, they need to speak to Ebay Customer Support.
Contacting them in the morning is best as they are more likley to be speaking to an agent in Dublin with more knowledge of UK banks.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)