Oneworld lounge recommendations for Hong Kong and Singapore

My view is that Hong Kong probably offers the best choice of OW lounges anywhere in the world. I would probably second Sid's suggestion, though the Wing is also good. I personally like the Qantas lounge in HK as well, depending on how long you've got or what you want to do, you could visit more than one. If you're leaving from T5 at LHR and you can access the Concorde Room then nothing else there gets close (bar set low mind). Ironically there are much better OW lounges at T3 at Heathrow, from where not that many BA flights leave. The SIN QF lounge sure gets busy at peak times, personally I'd say you're being a bit harsh, but I take your general point. Sadly your timetable means you will be heading through just prior to when the new QF First lounge is due to open in November. You can use the Emirates lounge, which isn't too bad. You can also access the BA lounge, which is bang next door to the Qantas lounge and is (usually) much less crowded, if you want a shower, its usually the best place to go in my experience. Unfortunately as your onward flight from SIN is with QF not BA you won't be able to access the Concorde Bar which is within the BA lounge.