Hi Kate . The quickest route up Ben Nevis is the Glen Nevis path and I'm afraid it's a four hour staircase , more or less the same angle of slope all the way up . You are starting at pretty much sea level and you have the full 4000+ ft. ascent to the top . The quickest route up Scafell Pikes is from Wasdale Head near Wastwater . Again you have the full 3000 ft. ascent . The quickest route up Snowdon is the pyg track starting in the Llanberis pass . The road rises to 1100 ft so you only need to climb 2400 or so . You haven't mentioned when you will be doing it , the days now in August are getting shorter . The best time to do it is in June , it's light at 4.30am in Scotland in June . Best of luck , I hope you enjoy it . For preparation do loads and loads of walking . The one drawback is that the thing tends to be a bit of a rush and you don't get to see the best of each mountain , all three of them have a lot to offer . If you do enjoy it , then I would say go back to Ben Nevis in the future and ascend it by the best route - from the Fort William golf course following the path up Carn mor Dearg , round the Carn mor Dearg arete and on to the summit of Ben Nevis . That way you will get to see the mountain in all its glory and you will get the best view of the north face , the highest cliff face in Britain . If the weather is cloudy you will need a map and a compass but I hope you have great weather and a wonderful clear day - it will make all the difference . All the best .