@Edlandy
You mention "green lane" and "nothing extreme"
This springs to mind the image of a countryside track, overgrown vegetation, lumpy ground with lot of stones stuck in dried mud, the sort a countryside-loving dog walker or cyclists on ATBs/MTBs would go through. In wet weather, it is nothing more than just like a muddy playing field. Thus a good pair of walking boots would be suited to this type. If this is the kind you are thinking of, then AT (or 4x4) tyres are as good enough as any walking boots.
M&S tyres are kind-of more-like supposed to be the equivalent of wellington boots or snowshoes (image a tennis racket attached to the bottom of your shoes), some says it do have an advantage, others says it is a marketing poly, and they're really more suited to mud that's inches think and covers the whole of the tracks, or blanket Britain kind of snow (Or the images of WWII Germans blogged down in the mix of mud and snow during winter in Russia, springs to mind).
I would agree with most of the above members on some points, you'll be fine with AT tyres for nothing extreme, easy green lane driving, specially the members' suggestions on driving slow and such. Plus you're likely to do some driving on main roads (such as going from home to green lane), therefore AT tyres could last a bit longer than M&S tyres.
That's just my option. Thought if you were to compare tyres to footwear, hope it helped you to get an idea.