I want to thank everyone's input on this topic, I've received really good responses and advice.
I can happily say that ive successfully enabled WiFi calling by just installing a couple apps. No need for a pc or rooting. Now I have WiFi calling option in the sim card section of settings. Not sure if it'll disappear on the next sw update but, even if it does, it literally takes 5 mins to enable WiFi calling again.
Very happy
Quick question... WiFi calling is different to how other sim cards connect to the tower in this phone, right? Because during a call I noticed that it sometimes gets a bit distorted, like it would on a WhatsApp call. Also, if they turn off 3G next year, would that affect me?