The other one you can do, which I found useful is to do an up-and-down of PYG from Horton, then drive up to Ribblehead and do Whernside and Ingleborough (taking the walker's route, which is definitely easier than straight up BTW), but come down Park Fell back to Ribblehead. Then you get most of the climbing in about 19miles or so.
In some senses, because it's a quick race (because it is largely so runnable), it's worth doing some tempo-type running that you'd do if you were doing a Marathon - it's a long run both between PYG and Whernside and off Ingleborough to the finish.
My training this year will be largely targeted for doing London the week before. 3P will just be for fun....