If you look on TrailWise and the Norfolk Interactive (
http://localview.norfolk.gov.uk/lv_external/Sites/countryside/) maps that will give you some idea of what lanes are open and those that are not.....
Finding decent lanes often requires a lot of research so please bear in mind that some folk are not very willing to share routes etc unless you are known to them.....
Trailwise will give you limited search functionality unless you're a TRF or GLASS member. If you've not been green laning before please ensure you've read the stickies at the top of this forum section....
have fun.....