merlin45: Its common for pilots to just call "joining via the overhead" giving no indication of which RWY they plan to use
Isn't that the point of the overhead join, - to establish which runway is in use? Once overhead and it's established which runway to use then a call should be made announcing which runway the pilot intends to use.
Unless conditions dictate otherwise, there should be three calls; a joining call 5 to 10 miles out, an overhead call stating which runway they're joining for and a downwind call. If the overhead call doesn't contain information on the intended runway then those pilots need some education as that's the main point of that radio call.
If you're joining after an aircraft which has made an overhead join stating which runway they're using, there is no need for you to join overhead. By the mere fact the other pilot has broadcast his choice of runway you have in effect established the runway in use.
Unless you have strong evidence to the contrary that the preceding pilot has it wrong you can just slot in after that aircraft and join in the circuit direction behind them. Unless of course you cannot easily establish the other aircraft's position and an overhead join is considered a safer option.
I admit some pilots get their windsock interpretations arse about face and you do need to be careful when taking note of their runway choice. I try to take note of smoke drift, cloud shadows and wind lanes as I approach a field to get an idea on the likely runway.