I can entirely relate as I have just bought a CCM 404DS to explore muddy tracks and the rolling hills near where I live. If you have permission to go on private land – i.e. the local farmer’s field – you should have no problems and you can fill your boots (literally with mud!) If you want to go exploring further afield (no pun intended) and sharing space with members of the public, as a general rule you can’t ride on public footpaths and bridleways, as they are meant for people and horses only.
If you do then you could have the local police after you for all manner of offences. However, there are a bucket load of unsurfaced roads – often called green lanes – that you can legally ride if you have a fully road-legal bike – i.e. MoT, tax, insurance etc., and the ‘carriageway’ concerned is open to vehicular use.
As for where the trails are, a little bit of research can go a long way to keep you out of trouble 1 would recommend contacting a group like the Trail Riders Fellowship and speaking to the appropriate highway authority office so you can check maps concerned. There are some knowledgeable and friendly people who are only too willing to help and show you where to ride legally. Enjoy the mud!
Motorcycle Monthly March 2014