acesup as an IT technician I can confirm it is near impossible for a mobile company to police this.
They usually base it on people downloading LARGE amounts of data and then question them UNLESS the company provides the app themselves to tether in which case download an external one. UK Privacy laws would prohibit them knowing you're using an app to tether as the data goes through the app and as far as they get told, you watch a lot of Netflix on your phone
------------- There is a place to hide, it's in our minds.
Outfits:
Hi Gear Kalahari 8 (Plus porch)
Vango Icarus 500 (Plus enclosed front canopy)
Hi Gear Solus Horizon 4
Vango Banshee 200
Vango Dart DLX 350
Vango Alpha 250
Yellowstone Alpine 2
There are ways and means I believe in something called deep packet inspection, but from what i read some people have tethered without problems and others have problems when on unlimited mobile data