Cannondale Bad Boy is a nice city bike but its not setup for long days in the saddle.
The usual bike for touring roads and tracks in the UK is a touring bike, it has a comfortable riding position, tyres fat enough for tracks, bridleways etc and efficient enough for roads, good luggage capacity, low gears and isnt too heavy. The road-style drop bars are used for the variety of hand positions rather than to get low and aerodynamic.
The classic good value tourer is the dawes galaxy but there are a couple of other budget versions and plenty of different high-end ones. New ones start at about £800 .The used market should turn something up, esp through the Cyclists Touring Club. This is typical of a used budget tourer are excellent price.
Good brands are
Ridgback, Hewitt, Thorn, Edinburgh Cycles (Revolution).

It is important to get the right size and you need time to adapt to any new bike. Get some saddle time in through regular rides to condition your body. Endurance riding is less about athletic fitness and more about comfort.
Use a helmet and gloves (fingerless cycling mitts) to protect yourself in case you take a slide. Cyclist only crash one with bare hands, never again. Cycling shorts are probably a must , they are worn without underwear and MUST be clean. Cycling shoes and clip-in pedals are really optional.