In reply to ScraggyGoat:
I went down there many years ago, drove round a bit and then headed off. I guess it would be ok for one night but we were looking for somewhere for a few days and to be honest I didn't particularly like the look of some of the other campers. Might have improved since then of course. Then again, perhaps not.
There's also a couple of places adjacent to Brora, here's one of them: https://www.facebook.com/SeaBreezesBrora/
There's a municipal campsite at Dornoch which is actually quite nice for a municipal site.
I guess the other option is to just keep on going until you get to Thurso and stay in the municipal site there. I stayed for a night and it was fine, very handy for the ferry IIRC.