Tom / Scott - I think you'll find that they are all real fell races!
Look in the FRA handbook and you'll find Rivington in there as well as Borrowdale.
I think I've made this point before - speed, speed, speed - you need to develop it when young as you cannot work on it as effectively when you are older.
Check out the Billy Burns article in Fellrunner.
You can work on strength and stamina once you get older.
Put in some track work, and try some track races - push the pace.
Some photos from Dave & Eileen on
http://woodentops.org.uk