I don't book international trips. However, I do book a lot of personal and business travel for our company.
I never, ever, use a discounter. When you do..... you may think you are getting a good deal and sometimes it works out... BUT, if there is an issue of any kind, you are stuck with an 800# and no one to help you at the airport. Also, the discounted ticket holders are the first to be bumped from overbooked flights which in turn can make you miss connections, and be out more money to get to your destination or home.
When you deal directly with a major airline website, you can sometimes get a fair deal depending on when you book. You also get peace of mind that if something goes wrong, you have a better chance of getting it taken care of at the airport with the representatives from the major airlines. You at least have a person to work with face to face vs a toll free # where the person on the other end could care less what happens.
I have family that routine travels to England because we have family there. They too, never, ever book through discounters.
Good luck.