"Every effort has been made to trace all the copyright holders but if any have been inadvertently overlooked, the publishers will be pleased to make the necessary arrangments at the first opportunity."

wEIrd.
fix.
op

"Trace" isn't quite the right word. "Track down" or "find" would probably be better.

Also, I think, technically, you'd be better off using the subjunctive in that last clause to go with the if, but most native speakers wouldn't even notice.

Other than that, it's fine.

'Trace' is perfectly fine in this context, in normal British English. I would have placed a comma between "copyright holders" and "but".

'Trace' ist annehmbar in diesem Zusammenhang, in normale Britische Englisch. Ich würde ein Komma zwischen "copyright holders" und "but" setzen.

Apart from the slightly superfluous redundancy of "inadvertantly overlooked", not really.