www.landyzone.co.uk

www.lro.com

Both have good forums. Be warned though, they don't like 'JAP crap' lol. I'd lie and say you have a ninety or something

As above with green lanes or BOAT's (Byway open to all traffic) will be shown on OS maps - you can use:

http://www.multimap.com/maps

and click the OS map button once you've typed a postcode or something.

You should call and check if it has a Traffic Restriction Order on it first though. I'm sure no-one does...

Pay and play sites are the best though