Upvote:1
This will largely depend on the terms and conditions of both the travel agent and Etihad. This one of the reasons why it's much preferable to book with the airline directly: there is only one set of terms and conditions in place and it's clear which rules apply.
Etihad is fairly clear about this (https://www.etihad.com/en-us/manage/modification-guide)
Correct your name Title amendments and name corrections due to genuine typing errors (up to three characters) are accepted free of charge.
But of course they also state
Booked with a travel agent? To change or cancel a booking, please contact the travel agent or third party website directly.
So you should
not sure how the travel agents can justify charging £250
The travel agent can justify everything that's legal and in their terms and conditions that you agreed to when you made the booking. To be fair, most websites clearly state that the name of the passenger must match the name on the travel document exactly.