I've stayed here quite a few times and would highly recommend it, You're correct the access road is narrow with no passing places if towing but dont let that put you off, I have no problem in or out and use a large Mitsubishi and 20ft twin axle van, What I would recommend is that you either let someone walk down in front and ensure you have a free run in, the same coming out, Driving solo there are a couple of passing places if you meet another car.
------------- Doing as little as possible for as much as possible...
We have stayed here too a few years ago, I got out of the car and walked down when arriving with no problems then did the same when we left. It's not a long road.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.