I've recently borrowed a mountain bike to commute around 10miles a day and I'm really loving cycling again. I am looking to use the ride to work scheme at work when my first three months are up. I'm looking to get a bike that will comfortably suit the commute on roads but also to start training to do the London 100km race next year. What type of bike do you think I should go for? Will a lightweight hybrid do for this? Budget around £500.