Hi Dean
According to your explanations, we could understand that the problem is not coming from your brakes. However, if you have a limited slipper rear end, you have to remove the brake pads at both sides to be sure that is not a brake problem (if only one wheel don spin freely, the second one will be also affected). Do you have the same problem at the opposite wheel or is it at one side only? If the problem is at one side only, you can conclude that you don't have a limited slipper and you may investigate for a roller bearing problem (try first to remove the hub cap and untight the large nut to check the bearing clearance). If both sides are affected
your car is probably equipped with a limited slipper rear end and you can have a roller bearing or a rear end problem. Let us know the result of your investigations.
Bernard