Apple Watch Cellular with O2 Business

If o2 has told you that you cannot use it with a business account, that is their way of doing it. They set the rules for how they activate the cellular watch. Nothing anyone here can do to change it. You can use an Apple Watch without activating cellular if you wish when it is with the paired phone.

If your iPhone has the regular SIM as well as eSIM support, you can add a second line to your iPhone that you pay for, and then share that phone number with your Apple Watch. This is a rather expensive way to go, and it will just interact with the 2nd phone line, which may or may not satisfy your needs.

A GPS only Apple Watch can do Everything the cellular model can do as long as your iPhone is nearby. Since you say you need your iPhone 24/7 it sounds like the iPhone is never far away from you. And by nearby, I mean both devices are somewhere inside a typical 3-4 bedroom home (assuming typical wood frame constructions).

And a GPS only models does not care what carrier you are using, now what kind of plan you are using. It is just a very smart Bluetooth device attached to your iPhone, not unlike Bluetooth headphones, except it can do sooooooooo much more.

This is between you and O2 then. See if they have a plan that allows you to pair an Apple Watch.