Strong enough yes, how long it lasts or the quad for that matter when its over loaded with, posts, strainers, and a few roles of 300m sheep net!
https://multec.co.uk/shop/post-drivers/professional-quad-fencing-trailer/
https://gtectrailers.com/product/fencing-trailer/
If there is some kind of permitted access onto private land borrow a thermal and spot who's doing it. Ask landowner first if they have given permission to anyone. Theres a estate near here, 7000 acres no keeper, but a few folk have permissions.
Cheap pine, treated to make the moderately flame retardant. As for delivery when buying such things…..most builders merchants give you free delivery if you have an account. Main advantage of opening an account!