I've had water pooling under my mat overnight when i had a Laserlite. It happened even on dry ground in winter if the conditions were right. I put it down to condensation due to the mat not having enough insulation, and warm body heat condensing on the cold tent floor. Who knows?
I use that Wickes stuff now on all my UL shelters, and don't have a problem. Water can be forced through groundsheets with a low HH.
If water is coming through instantly, then it obviously isn't condensation.