Personally I use CX. The transit time in HKG is only about an hour and a half, which makes it one of the quicker total journey times.
If you are not too worried about losing half an hour then I always take the second CX flight out of HKG for LHR, it is usually less busy and I have often had a row to myself!
EK are OK via DXB, but just make sure that you have minimal connection time in DXB. The A340-500 has probably the best IFE system that I have come across so if you can't sleep you get every chance to catch up with the latest movies. They were a lot more expensive than CX, MH, or SQ for my last trip though.