I have to say (because I have a cold right now and am rapidly running out of suitable nose blowing type paper) double quilted with added Aloe Vera type chemical goodness.

Though I did once go to an interesting place that had oh so soft leaf type loo roll. It was fantastic. I've never been able to find it since :(

Of course I could mention works loo roll situation at this point which would go along the lines of "whatever isn't suspiciously damp".