If you are looking to complete John O'Groats to Landsend or do a challenge like this, here are links and information we have used which may help you in your planning:
Training
http://www.surrey2012.info/assets/documents/cycling-road-race-route-map - Olympic Route
http://www.bikeroutetoaster.com/ - Has some good routes mapped out
http://www.cycle-route.com/ - Find lots of UK cycling routes
http://www.mapmyride.com/ - Has very good app for tracking your training progress
Route Planning
http://www.mapmywalk.com/ - Works out your mileage and gradient
http://saddlesore.weebly.com/route-maps.html. - Another route/ blog with lots of info
http://www.rideacrossbritain.com/ - Deloitte's 10 day ride across Britain
Bikes and Accessories
http://www.decathlon.co.uk/EN/ - Great for bike accessories
http://www.evanscycles.com/ - Offers a wide range of bikes on discounts
Hotel Booking
http://www.travelodge.com.uk/ - Cheap nights accommodation
http://www.booking.com/ - Wide range of hotels
http://maps.google.co.uk/maps?hl=en&tab=wl - Type in place name follow by B&B in google maps and lots will appear
