Hi Ian,
The France/Spain borders are usually unmanned and you just drive through. Occasionally you can see police cars looking for someone but they are unlikely to stop an obvious tourist. Spain expects you to have 2 warning triangles, spare bulbs and reflective vests.
Sorry don't know the site, we usually stay at St Jean de Luz just to the south as we know an all year site there. You probably know that Biarritz is a large well established resort. Watch out for sleeping policemen in the area, they seemed rather fond of those last time we were there.
Hope you enjoy it,
James