I use Skyscanner as a guide, then deal with the airline direct through their website. I pay the airline direct by credit card, as extra protection of my money.
Generally I've found Emirates or Etihad to be best value, combined with sensible journey time (from Manchester).
Last year I flew twice with Emirates (half the journey on an A380) and once with Etihad.
I'm going with Etihad again, early September. Cheapest flight I've ever bought, but using a 'promo' code.