A few questions regarding tyres for my F78.

The american SUV road tyres that it came with may not pass the next MOT as they are a little perished and one has a small slice in the tyre wall.
I'd like something like General Grabber AT2's as I do some light off-road work and intend on doing more (volunteer woodland conservation e.t.c.)However I do a fair amount of mileage to work and back daily and various other places too, all on-road. Would AT2's last very long?
If they are not the best option, does anyone have a recomendation of any other tyre type which I could look into? And, most important of all, can anyone point in the right place for price, as getting ripped off is not an option after x-mas!