So I run the test. No advice, such as to reboot my PC, close other web browser tabs, advise if I am using Wifi and make sure that nothing else is using my broadband connection.
I am suspicios of the latency which comes up as 16-20m/s compared with more like 5m/s that this web site records. The recorded up and down speeds of 500+ mbps are credible, but then I find that I can't select my broadband supplier, Gigaclear, from the drop down list to submit the results.
So can Which build up a sensible picture of the status of broadband across the country if they exclude results from one of the fastest, but small, suppliers? I am inclined to think this is not possible.