When I joined the (then) Strathclyde Police in 1982 I was issued with a whistle on a length of chain. The proper way to wear it was to hook the chain onto the button of the left breast pocket of the uniform tunic, then across to the top centre button, then downwards to tuck it away into the tunic below the 2nd button. After a few months, you soon realised that the whistle was redundant (thanks to the invention of radio communications) and so it was dispensed with. I always did wear the chain though, for the sake of appearance, but there was no whistle on the end of it.
As to the question, do they STILL carry a whistle? I don't know for sure but I very much doubt it! Traditional uniform and superfluous equipment has been done away with.