Unimog Club UK

As far as I can tell the only restrictions worth noting are that you cannot carry goods, or drive on the road for business use with red diesel. So if you were to drive it to work to do a paid non agricultural task you would have to run road fuel, Any products of that work unless for your own farm cannot be transported there/back.

There are various opinions about what you can get away with, but it's a bit of a grey area.