And which one?
Or, what else should I be looking at?

I had the exped ul7 for yrs it was great but i know use the xtherm from thermorest and love that! It warms up straight away with ur body heat

I’ve also got a Synmat UL7. It’s warm enough for most of the year in England, light and packs pretty small.
I do however still prefer to sleep on a Thermarest ProLight and still carry it often despite it being a bit bigger and heavier.

I was recommended the Exped DownMat Lite 5 by multiple people, when I asked a while back. I've been very happy with it so far.

I use an Exped Synmat HL all year round.

Various Expeds for me and I like them all. I think it's just a matter of matching your budget and requirements to the R value and weight of the different models.

I have the Synmat HL MW which is nice and comfy, it's a bit of a luxury mat for me when I'm not going too far. It's nice and wide but it's not the warmest.

I've always used Thermarest and have been really impressed by their customer service. My neoair Xlite which had done over 300 nights had a couple of seams fail producing a large bulge in the mat. After an email with a couple of photos I sent it back to Ireland and received a new replacement free of charge within a week.
I've since upgraded to an Xtherm and the difference is amazing. I'm sure I could get away with a lighter sleeping bag now.

Earlier this year Thermarest changed the testing method for the R values of their products giving the impression that the newer versions of their mats ( improved inflation nozzle) have a significantly higher R value than the old models. This is not the case, they are exactly the the same with the exception of the nozzle.
You might be able to find old stock at a discounted price.

I have found the OEM Traverse IMX mat really Comfy and warm, at a budget £45 +£9 for the Pump dry bag. Good value and approx 450g. Available at go outdoor.
Since All these mats are delicate I can not justify £ triple figures.

https://www.gooutdoors.co.uk/15904974/o ... t-15904974

https://m.youtube.com/watch?v=vJpP-bfFzV8

I used it a, weekend ago when the temperature dropped to below 10°c, I had a thin 3mm mat under it to protect it, it was just an underfloor insulation off cut, of little insulation value. I slept in all my gear in a wet sleeping Bag VANGO 3 season Synthetic. The only thing that bothered me were wet feet...
450g and smaller than a coke can... Why spend more...
It is not insulated..

Thermarest for me and I have both a standard 3/4 and full uberlight, both are roughly the same weight.
The uberlite is very noisy, the standard is also noisy but less so. Both are very light.

Alplit Cloudbase I found OK recently mind. Only 1 night yet. Not thermal, not anywhere near as light but packs fairly small.
No noise and seems to hold its shape better, so although not as thick it is still comfortable. Much cheaper too.

492g - cloudbase
217g - 3/4 Neo air
254g - Full uberlight

All w/out bags, just use a hair band.