Those that use esim, can I have esim with one provider and a pay as you go with another provider? I want to switch to O2 for my main contract line but I figured I might as well keep my EE pay as you go sim in the phone for business use?
Yes you can use it in this manner. I have my phone setup this way to get the better coverage using 2 different carriers.
The hard part is making sure one carrier supports eSIM for the plan type you want to use. Since all of the carriers support regular SIM's that won't be an issue for that part.
I'm not in the UK but I believe EE supports eSIM. I'm just not sure if it's for all of their plans so you need to check on that first. I don't know about O2 but if they don't support eSIM then you should be able to use a physical SIM.