Air mats are complicated to produce.
The risk to throw money out of the window is very high if you buy a cheap mat without very convincing recommendations.
In your financial situation I would buy nothing else than a Therm -A- Rest model because they have a well proven client service. They really change failing products without making problems.
Look it up yourself for Britain. I think it's 25 years warranty here and life time in the USA.
I recommend to save the money elsewhere, but not at the mat.
If you have to throw away a cheap mat every year, you reach the price of a Therm -A- Rest pretty soon!
One can buy a basic Therm -A- Rest model and put a used army roll mat, closed cell foam, underneath in winter conditions. Or if you find it a used German army folding mat, that is light and very compact packing.
I always put the German army mat under my air mat in order to protect it.
The German army mat is my ground sheet in most cases. Onto it I put the bivvy bag or directly sleeping bag and sometimes the air mat, which I don't use always.
I don't know how exactly is the ground in your area. If it's soft you can tread with a robust mountain boot a hole for the hip into it as a side sleeper. That's how they did it before they created the air mats.
Once you have learned how that has do be done exactly it's very comfortable.
Of course that can be done under a too thin airmat too.
The German army mat exists original only as a used article, is getting rare and costs in Germany between 20 € used and 30 € new old stock if you find it, what's unlikely.
Here we have the much sought-after genuine Bund vertically and horizontally folding sleeping mat. These mats are very thin, at around 4mm, so added comfort is in the 'bare minimum' category. All mats are ex-works and will be refurbished and repaired in various ways. Ascetically not for the...
www.endicotts.co.uk
Maker was Molan in Bremen later called Trecolan. It must be written on the label that's moulded into a corner of the mat.
Avoid the cheap new sold copy!
Multimat makes a quality copy of this mat because the German original is out of production and British parachutists wanted it. Multimat is the maker of the British army roll mat too. You can look up the specifications there, before you get it used somewhere else.
Sleeping mat, ideal for global backpacking
www.multimat.uk.com
Sleeping mat, for durability on unsupported expeditions As supplied to the British Army Meets the requirements of NATO stock No. 8465-99-130-5904 Manufactured from premium-quality, polyolefin foam Eyelets and lightweight attached webbing
www.multimat.uk.com
Sleep Mats:
www.endicotts.co.uk
Have a look through all the endicotts offers! Would I live in Britain I surely would buy most of my equipment there.
They are well assorted, the prices are low, the stuff is surely always good.
I bought most of my equipment in similar shops