WOO! I'm back!
What a fantastic place. I didn't see everything by a long chalk (walking to Ormaig and drooling over it [perhaps that's what the black stuff is] accounted for half a day), but I saw a lot. Plenty to go back for, anyway :-)
I whizzed over to Arran on the last day and managed to see Machrie Moor, the rock art on the ridge and another circle. Ferry times and having to drive from Kilmartin to Ardrossan to get on the ferry took a big chunk out of the time available.
After seeing the weather in the northeast 'm very glad that I didn't go for Aberdeen!
Once again thanks to all for the help & tips.