Sleep disruption

It might be a coincidence but I've been having problems sleeping since starting my training for Trailwalker. I would have thought that after getting up at 05.30 every week day to do 30 minutes on the treadmill before work, and then writing until 21.00 each evening, I would be dead on my feet by bedtime but I'm regularly reading my Kindle or playing solitaire on my iPhone well after midnight. I'm looking forward to a lie in tomorrow - I don't intend to do any exercise before 08.00 as it's the weekend! Mum and I intend to walk along the beach from Hayle to Godrevy and back and the plan is to step the training up a gear next week.