A very warm welcome! You will find people pretty engaging and helpful here. Even if we fall out occasionally (normally about something stupid like I'm interpreting things differently to EVERYONE else lol!)
Most common is pretty flexible a term. I would say hold them as often as you can commit to acting on what is raised and, if you're finding that f all is raised in a quarterly meeting, that would worry me. Especially in the UK. As a Brit myself, I know that either people have A LOT to say or they've stopped raising things for a reason.
So personally, I'd stick with quarterly if that's your current frequency and if you're getting nothing, bring something to it. A few open questions. "What does it feel like to work in your area? Do you feel supported? What would make your job easier?" etc.
And bring cake. Everyone loooves the cake.
Also bear in mind as you're BRCGS certified, this could be part of your culture improvement plan (you still have that in packaging I'm pretty sure?) Use the sessions as an opportunity to call out positive behaviours perhaps or note areas which might need to improve but have an honest chat, why aren't they good now?
As for what I see in other plants? As often as weekly, monthly is common, not at all is not uncommon either. Weekly is probably too much. Monthly is probably pretty good for most plants. Not at all (or, sorry) once a year is not enough in my opinion. Even if all you do is eat cake and have a chat.