Three are removing the unlimited tethering from the Sim Only 'One plans' from tomorrow and the limit will be replaced by 4GB.
This is your last opportunity to pickup the sim card with the unlimited tethering facility.
Extract from Three Ts&Cs
This seems very clear new contracts pay monthly 2GB, new Sim 2014 plans 4GB.
It says Personal Hotspot (tethering) can still be used on older 1 Plans (that allowed it before of course).
Personal Hotspot on your phone.
Using Personal Hotspot is when you connect your phone to other devices to use it as a modem so they can access the internet. It's also known as 'tethering'.
All our new Pay Monthly phone plans and new SIM 2014 plans include Personal Hotspot. If you have a limited data plan, using Personal Hotspot will use data from your data allowance. If you have all-you-can-eat data, you have a Personal Hotspot allowance of 2GB for new Pay Monthly plans and 4GB for new SIM 2014 plans. This means you can use the internet when you're out and about with other devices including laptops, tablets and games consoles, just by connecting them through Wi-Fi or USB to your phone. You can also use Personal Hotspot on all our older One Plan plans including our one month rolling SIM plan.
If you run out of your Personal Hotspot allowance, or you’re on one of our older Pay Monthly plans, like the Essential Internet or Ultimate Internet Plan, you’ll need to buy an Add-on. You’ll then get a Personal Hotspot allowance. You can only use this allowance in the UK.
To find out what Add-ons you can get on your plan, and to buy an Add-on, visit your My3 account on your computer, or open My3 on your phone and select Buy Add-ons. Unfortunately some of our older plans aren't compatible with Personal Hotspot Add-ons.
Our Pay As You Go plans don't allow you to use Personal Hotspot. See our Pay As You Go terms and conditions for more information.