Freelander 2 (LR2) Stuck wheel nut

Had my 2009 Freelander 2 for a couple of weeks now and decided to check the wheel nuts as it’s better to deal with a stiff one at home rather than at the side of the road. All were really tight but one on the back will not move even using a 3 foot breaker bar and quality 6 sided socket. I did think I had snapped the stud at one point as the nut seems to wobble but it seems to be the stainless steel outer shell thats come loose, the nut will no turn, never had a stud break but I imagine it would turn and pull out ?
Any tips to get it off? I have a impact wrench that you hit with a hammer that I might try next weekend but failing that the car is booked in for the timing belt to be changed in a couple of weeks so I might let them have a go at taking it off the way it probably went on, with an air impact gun.

Probably best to purchase six new studs and nuts before you go further, nut will need cutting off and stud replacing