Richard,
We lived in the north of Scotland from 1980 - 1987 and cut our caravanning teeth in the highlands. The site at Ardmair, which Maureen mentions, was one of our favourite places and we went there many times. If you like walking in wild places, in spectacular scenery, the area above Ullapool takes some beating. I remember climbing Stac Pollaidh (Stac Polly) which isn't too far away and in good weather there are great views from the top. There is a visitor centre at Knockan, again with great views.
Further north on the A835 there is a site at Scourie, which has the most incredible sunsets. Handa Island is not far away.
We have stayed on the site at Thurso, but this was all several years back and we don't know how the sites may have changed, but by all accounts, the site at Ardmair remains as good as it always was.
Another site we can recommend is Kilvrecht at Kinloch Rannoch (turn off the A9 on to the B847 at Calvine, head for Trinafour, pass through Kinloch Rannoch village to the southern shore of Loch Rannoch. Kilvrecht is a Forestry Commission site on the left, along the southern shore of the loch. No bright lights and skittles here! It has toilets and water, but no electric hookups. Great caravanning set amongst wonderful scenery with lots of walking from the site. A drive along the lochside, joining up with the B846 will bring you to Rannoch Station, on the edge of Rannoch Moor, one of the most photogenic and remote railway stations you will find. When we were last there a tea room had just been opened where we enjoyed a mug of tea and home made cakes. But beware the dreaded midges are in abundance in the summer months!
We shall be setting off with our caravan to the north of Scotland from East Anglia in a weeks time to celebrate our 40th wedding anniversary. Hope you have a good holiday too!
Pauline.