Having been in the sandpit myself for months on end, I am afraid that I don't agree totally with your post.
We had no need for civvies, or any with us if we'd needed them anyhow. We neither had a wish to wear them or were ordered not too, just in case someone had smuggled some devils-cloth to the sandy places we were operating out of. At the end of the day, if all you have to worry about is what kind of clothes you are wearing, me thinks you have lost some sense of perspective.
PS - My grandad was in Queens Royal Lancers in WW2 and spent most of his war in Africa. He had to wash his clothes in petrol, because there was more of that than water. Imagine how pished off he would have been, had he needed to wash his cK jeans (if they had existed in 1941) in petrol. Perhaps sticking in rig is a good way ahead.