Yes-as GFL says there are grayling throughout the Clyde system.
I have had a 44cm grayling 100yards up from Wolfclyde Bridge and another 44cm fish 100 yards down from the bridge with plenty of other good grayling in between. (hope I can mention it now, the river is closed after tomorrow)
They haven't moved away from these areas,they are still there,but you have to be on them when they are feeding.
It could just be for 15mins. in that day and its usually at last light.
Give all the known grayling spots a go, cover as many as you can and just hope that you hit them when they want to feed.
However if you are fishing maggot you could go to a known grayling area and loose feed to induce the fish to feed.
Nothing against that method-Ive done enough of it in the past but I am now fly only----Peter