Two sites you might to try
Glenmidge Smithy, at Aulgirth. Aulgirth is approx 8 miles north of Dumfries on the A76. The site is approx 3 miles from there, it is very quiet,spotless, with electrics,toilet and shower and only takes about 12 vans.Full details can be found on the Visit Scotland web site under Dumfries & Galloway. The other site ia Caravan Club CL at Sanquhar approx 10 miles further north on the A76. I have never been on this site (just a little to close from home)but it looks very nice and there is always vans on it. This site is just off the main road and is easily accessable. The Ranch at Maybole is only about 1 1/2hrs from here..
Hope this may be of some help
William