I think the Freelander 15" rims are probably only 6x15 at most (6" wide), which probably isn't wide enough to run a 10.50 on. You can get both steel and alloy 15" rims to suit a Freelander but either will have originally been fitted with 195/80R15 tyres which are a hell of a lot smaller - 27.2" diameter against 31". I therefore think that even if you can shoehorn them onto the rims without your insurers having an epileptic fit, they probably won't physically fit on the vehicle without wiping out large chunks of the bodywork every time you go over a kerb
If you want AT type tyres then your choice is pretty limited (if any) - the 17" size for a Freelander is a 225 section IIRC, and the General AT2 doesn't come in one that small and I don't think the BFG AT does either, though I haven't checked. If it was me I would go for 15 or 16 inch rims which can probably be found quite cheap second-hand, and that gives you a much wider range to choose from, of which my choice would generally be the AT2.