Must admit I don't take much notice of the law in Scotland. There has always been a theoretical freedom to roam, but sites are often so isolated I always ask at the nearest farm house if the vibe doesn't seem quite right - if practical, of course. Never been turned down yet and have got quite a few great insights with speaking to the owners... particularly on the west coast.
My advice would be.. if the site is near habitation, ask out of courtesy. If not, go have a look and be very friendly and co-operative should someone turn up.