I own a Citroen C-Crosser 4-wheel-drive with 18-inch wheels and 225/55 R18 tyres. I will shortly need to replace them. The only criterion is I pull a caravan, off grid, which means we use ordinary fields quite often. I am having difficulty in finding the correct tyres to replace the originals and would welcome your advice. We use the caravan all year round, so attend rallies often in quite muddy venues and drive in ice and snow.