Sleeping Mat: Light, small but comfortable?

I'm looking for a new sleeping mat for the Summer. I'm planning on using it on longer trips where I'm carrying all my gear in a 40l backpack for up to a week. So weight and packed size are crucial.

But, I need a bit of comfort, I tend to get sore hips from side sleeping on my current standard Thermarest (which is bigger and bulkier than I'd like to carry really). But I am quite a warm sleeper and will have a down bag with anyway.

Reading old threads on here the exped down and synthetic mats seem to have a good rep, but my budget doesn't really extend that far. I'm looking for something under 50 quid really.

I've seen the Exped Airmat 7.5
and few offerings from Alpkit such as the Numo and the Airo 120.

Any thoughts on these? or alternatives?

Uninsulated air mats? Will pack light and should be comfortable. The caveat is that you'll be getting virtually no insulation underneath you - the down in your bag will be compressed and so not offering much warmth.

So it could be a problem cf warmth in Spring/Autumn. Or maybe not with some foam etc under it.

If you can stretch the budget a bit there are some semi insulated air mats (less than the down ones) which would be 3 seasons fine.  Depends what you're trying to do I think

Yeah. It's really just for Summer use. I have a thermarest which is fine for the rest of the year (I wouldn't get away with packing so light in the Winter anyway!)

I'm liking the look of the Numo and the Exped Airmat, they seem to fit the bill, but anyone have experience of either?

Only comments I've read on the Numo were on Traksterman's blog and he seems to have binned it.

Not under £50 but worth every penny; Thermarest NeoAir. Excellent piece of kit.