Oh and PS watch out for some NSC members in their cars; apparently cyclists are fair game and should be run over for not paying Road Tax (which hasn't existed since the 1930's).
1. Firstly, train for it! Make sure your training includes hills as this is what will be the hardest on the day.
2. Keep eating throughout - bananas & cereal bars.
3. If you have to use a mountain bike, consider (if you haven't already got them) investing in some SPD pedals and shoes. You can...