Could I recommend Where's the Path - a brilliant website which allows you to view OS mapping alongside satelitte or any other type. Making it brilliant for route planning. It also has a helpful route function, giving bearings, altitude, route height gain charts and distance/time info. It's been brilliant for me - both as an outdoor enthusiast and as a GCSE geographer. Find it by googling 'where's the path' or with the link below.
Please feel free to reply with your impressions.