Hi Nigel
Everybody has their personal likes and dislikes. I would say be sure to not miss Andorra. I love it there - not everyone does, because the main road through is rather busy, but the mountain scenery is wonderful. Also prices are low(er), and there are some tax free bargains. Petrol and diesel prices are probably second cheapest in Europe, after Gibraltar.
Last time we stayed at Frontera Park, which is actually in Spain but only just across the border. It is in the Camping Cheque book, very conveniently located. and nice for a few nights stop.
There are plenty of other interesting places in the Pyranees, too, especially if you like mountain scenery, so if you have not been before, almost anywhere would be worth exploring.