My father served in the army during the Northern Ireland years and used to tell me he was forced to leave his uniform at the barracks when out on leave. There was a risk that they would be attacked in the street by the IRA or IRA supporters...
I think the civilians don't have as much trust in the armed forces as they used to, especially with the protest against the Iraq and Afghanistan wars. They don't seem to realise that these soldiers are sent where the govt wants to send them, they don't have a choice.
Saying that, I've walked around in military outfit before, never had any problems. I've seen plenty around Glasgow and never seen any problems, and most military personnel I know have a habbit of telling everyone they meet!