A couple of things. My Exped has a puncture but I can't find it, it's good for around 4 hours of sleep before it's flat. I spent the best part of an hour trying to find the leak in the bath but no luck. Any magical ideas?

On the same subject, I'll be doing a bit of riding later this year in areas with lots of spikey plants, any ideas for more a robust (puncture resistant) mat or do I make a return to closed cell foam?

It could be the flat valve - blow the mat up, wet the 'valve plug' with a bit of spit. Fit the plug and then twist it an 1/8 of a turn and see how you go on. Hux put me onto this a few years ago and it was spot on.

Cheers. Done, I'll see tomorrow if it holds air.

If that doesnt work, your next option is probably the soap sud test. We use it for drysuits (think cold water diving or air/sea rescue etc)

Lay out a sheet of plastic in the sitting room. Inflate your mat and put it on top, bottom side up. Chances are the hole is on the bottom.
Mix up a good soapy mixture with fairy liquid - dont try and use ecover or any of that hippy bollox, what you want is a proper syrupy mix, fairy is ideal. Wet down the top of the mat, liberally. Put on a film, have dinner, make whoopee, whatever, but keep the top wet till you either see bubbles, or you dont see bubbles. You say 4 hours? You'll probably see pin-prick bubbles in less than 20 minutes. Make sure you do the seams and around the valve.

Still not found the hole? Do the top side the next evening. Once you find the hole, wipe the mat down and mark that spot in big X with dress-makers chalk. What do you mean you dont have any dress makers chalk?

When I got my dress taken in last year it ended up too small around the hips because the dress maker had used up all her chalk fixing sleeping mats.

Took me for ever to find the hole in mine. After I found the valve was 1 culprit i blew it up as hard as i could,stood it up in the shower and did the soapy sud test. Found 2 microscopic holes,1 either side of the top of the mat halfway down. I reckon it was caused by the zips on my shorts and rolling round getting changed!