Not sure if this has been covered elsewhere but if you are aiming for a BG in 23.59 you should be aware that the path from Portinscale across to Keswick is closed. You have to stay on the path up to the main road and come in to Keswick along the B5289. Only adds a minute or so (depending on pace) but if its nip and tuck at the end, worth remembering.
Having said that, if someone finished in 24.01 due to the extra distance is some 'considerate' time keeping at the end acceptable?
If you're going through Hell - keep going! Winston Churchill