Why not to go for buying cheap electric under floor heating?
“You get what you pay for”.
Cheap electric underfloor heating has a hand written label on them detailing the wattage and resistance of the cable. No CE or any approval symbol of any type printed on it. The earth protection is a single strand wire.
A good quality cable mat is almost the opposite of the above. Most good quality mats come supplied on a cardboard tube to protect the shape. It will have a proper sticker on the wrapping.
You shouldn’t install a cheap mat just because you might be saving £20, you will only end up doing the job twice – which in the long run will cost you more.