Welcome to the forum E.Canon2014
All good advice above and I can’t really add anything more on PE, excepting to say I’ve avoided BA “Y” at all costs. Having said that, I’ve got the luxury of a having a stash of avios to UG to PE with and PE is good, but probably not worth the difference.
Anyway, I’m someone who travels EDI- HKG fairly regularly and because it’s for leisure (also visiting a mate) with other mates we’re quite cost conscious. Why spend money on flights when you can spend the savings in Wan Chai and LKF : )
My advice, choose your dates and create an account with Skyscanner. They will update you with prices and occasionally a great deal will pop through. For example a few weeks ago they quoted me China Southern via Beijing , on closer inspection , the AMS to PEK sector was actually on KLM. Maybe it was because there was a 24 hour layover in PEK on the return leg that pushed the price down to £352 return!!
Sadly my HK mate and his family are selfishly vacationing at Whistler, so I didn’t take advantage! : )
So, if you have the time to research, keep an eye out for codeshare flights. You might just find a cheap AF flight and end up on a CX plane !