Ok mats, have tried the closed foam ones (yuk)
Have had the cheap self inflating Argos one with inflatable pillow (ok about 3cm thick but cover not attached to foam so if you over inflate prepare to foll off) full length is too big and heavy.
Opted for the 3/4 length gelert quality one (and pm ogy if your interested lol) and i think was 4.5cm bit thicker but colder and less comfortable on the legs, but still not enough padding.
I have now gone for the daddy of all sleep mats :
http://www.sailgb.com/p/exped_downmat_down_filled_mats/Warmth, 9cm of height, small pack size and also fits in my bivvy bag along with sleepingbag, also means i can carry a lighter sleeping bag. Not for all tastes, but after 16+ miles over hills and mountains i would much rather carry the extra weight and have a great nights sleep.