If you start in EU you will save a lot of cash in the dreaded APD http://en.wikipedia.org/wiki/Air_Passenger_Duty

Try Mileage monkey http://slfft.org/, but may not be up to date, espically for QR
Your itinerary http://slfft.org/mm/award.htm?owe=LH...B-LHR&cabins=y (ignore errors)