I thought you might mean the StreetView line but it's blue on the Android phone app.
Should be hard to get lost with the beck there.
Your route is interesting in that it ascends half way up the fell earlier than the route I've plotted. I did think about attempting to climb the fell there but I wasn't sure if there was a path and decided to plot a route following your haroldstreet.org.uk trace instead.
Not sure what you mean by ascending the fell, the whole thing is a valley walk unless you are planning Murton Fell too! The Warcop Range Trace was recorded live in 2015 using my current Garmin so it is good gen but it comes into Scordale from Swindale. Walking up to foot of Swindale from Hilton is easy as there is good track. The trace continues all the way up to Scordale Head before it climbs up onto Murton Fell. Going up onto Murton Fell may be a step to far for you at present, probably better to follow the beck back down. The up and back used to be a milk run for Mrs N and me.
The range is divided into areas, some for live firing - mortars, grenades, tanks and such. The area behind as far as Mickle Fell is the overshoot. Scordale is on the very left hand edge of this area. Murton Fell across to High Cup Nick are used for soldiers running around, no bullets. The red flag is at the entrance to the range in Hilton. Sundays are usually good days and there are guaranteed access days too, published on the web. Range activity times are also published on parish noticeboards, we had one in Brough near the shop - there will be one in Appleby, probably by the Tourist Office in the town centre. If you are unsure, the lady in the Range Office was always helpful - she sorted out my legal walk up Mickle Fell. More information and phone numbers here
http://www.murton.org.uk/warcop-range-information/4594028687PS forgot to answer the flag at High Cup Nick. The Nick and the PW are not in the range. The red flag is for info if you thinking of entering the range which is S of Maize Beck and the top of Murton Fell- the edge is marked by big signs at intervals.