As mentioned above, check out the herts lanes and essex lanes threads. I am sure you would be welcome to join us on one of our outings with the proviso of having recovery points and basic recovery equipment.
Get yourself some OS maps, or have a look on multimap.com, changing the view to 'OS Map'.
And the advice from most of us would be 'don't go alone' It's not only getting stuck that could cause problems. If you break down on a lane, it is more difficult to get recovered or found by the rescue services.