Anyone got any recommendations for the best value for long-haul flight search engines/agents?

[ricekrispi]

Just that really, I know about Skyscanner but I'm not sure where else I should look.

www.kayak.com it also adds several other search engines unless you ask it not to. Found some good bargins there and you can use filters to refine things like major airlines only, flight times, etc

Trailfinders are very good.

google flights as well

Do not rule out using the airline's website.