What is the reason why you want to know what people use?
So developed a swivel that to your brushes ,even onto doodlebugs.
Was seeing what sort of connection to use on it.
Have also asked on a few FB groups.
Not only UK but USA, Canada, Australia few other countries.
Regarding connection on WFPs to the brushes genially EURO THREAD.
But the Quick-LoQ type connections have also become popular.
So it would not be practical to have two separate swivels one that has a Euro thread and another Quick-LoQ type connection.
Developed a duel connection that will take Euro thread and/or Quick-LoQ type connection.
This way if you like using Euro thread connection you can.
And if you choose to get a Quick-LoQ type connection just get one half of the top angle adapter.