I don’t know the place or the people, so apologies if some or all of this is useless / ignorant / already in the process of being done.
There’s lots you can do aside from being passive.
Have you made contact with the ROW officer at your local authority?
Have you talked to the local horse riders? If there’s no immediately visible organisation, just ride up to the local livery stables and ask – once the riders get over their surprise, they can be very helpful, and I’m guessing they’ll be interested in helping you out with contacts if they are having the same problems. Bear in mind horse owners tend to be very well connected types.
Also look up your local Countryside Access Forum and see if you can get some questions about the wood put on the next meeting’s agenda – it gets widely read (well, certainly at the Surrey CAF). Meetings are quarterly.
You might also want to speak to Ian Warby at CTC, and other local landowners who may know the guy.
Bear in mind that some landowners are not that ‘up’ on liability issues, and see horses, cyclists et cetera as a potential risk as much as anything else. This guy may think he’s doing the right thing – certainly he’s not physically blocking access yet.
There’s lots you can do if you stay polite and positive and get organised. I’ve been involved over the last eight years or so with talking to local landowners and land managers, and, while it takes time, it brings a lot of rewards for mountain bikers. Getting them to realise we’re not a bunch of two-headed louts is a great first step – and it sounds as if at least one local landowner is already there.
HTH – and best of luck.