Daifly: Can anyone at BA tell me whether there's lounge access in Bangkok for Club/Silver when at BKK for the 3.5 hours on the Friday night LHR-SYD please?
Leaving the anecdotes to one side ...
Assuming you are flying Club World and/or are BA Silver, the answer is yes. I think that BA uses the Qantas Club - but if it doesn't and you don't like it, you can get into that as BA Silver anyway.