I use a farm outside Kilbarchan, about 10 minutes off the A737. Its £300 per annum and its not covered but well laid out, good hard standing, water available for washing etc. You need to pass the farmhouse to get to it and its closely watched (if you get my meaning)and ideal if you want to pick up and get on the M8 (to venture east or west) or head down towards Ayrshire.
If interested PM me and I can give you the contact details.
Tommy