Back to the Milntown Cottage issue. The name was used in 1963 when Tony Godfrey crashed there in the 250 race, and was the first person picked up by helicopter.
I have always used  "Milntown" as the actual cottage, the white one on the left hand side on the right hander. The next right after the "Glen Audlyn" jump, has always been known (in my circles) as the "right hander after Glen Audlyn".
The left hander before Milntown has of late been known as "Sky Hill", as Alfie Noakes correctly states, but I don't know for how long this name has been used.
I'll have to do a bit of work to see when "Milntown Cottage was first used, but I have never read of it in any pre WW2 reports.