Here is a review of the SynMat Hyperlite by Ian Finch in the UK. SynMat Hyperlite is the lightest insulated mat available anywhere. 

 "I’ve certainly found sleep deprivation, for whatever reason, can turn an experience in the wild into a tired, aching adventure requiring a morning dash to dip in the nearest mountain stream. Ultimately what you’re sleeping in and what you’re sleeping on plays a crucial role in making this experience as comfortable as possible."