Sure @BertieBotts happy to tell you more but with some caveats - I can only speak about my experience in my current role, it's my first UXD role and I've only been in it 18 months so I am very much still learning. Also, I work in the public sector so UXD roles in private sector/agencies might be different.
Do you spend all day in front of a computer alone, or is there quite a mix with client interaction? What would you say the percentage is?
I currently do spend all day in front of a computer alone but that's only because I've been working from home since March 2020! 
But in general it's very collaborative, I spend quite a lot of time in virtual meetings or design sessions with colleagues. Because of Covid all our testing is virtual too but in normal times I would be in face to face sessions with users observing what they say/do. During the testing phase of a project, we'd do several sessions over a week. Overall I'd say it's about 50/50 working with other people in some way versus working on things by myself.
Is it really really OK not to do coding?
In my organisation we use either a standard content management system or software called Axure to create prototypes - if you know how to use design programs/can generally pick up new software quickly you could do my job no problem! However in other roles you might well need to do some coding, I don't know enough about how it's done elsewhere, sorry.
I have history in graphic design and customer service, would those things be useful?
100%, that background would be a huge advantage. Several of my colleagues are trained in graphic design and I am considering getting a formal qualification in that area. Customer service skills would really help with doing the testing side of it too.
Lastly is it only about websites and apps or does it spill it into anything else as well?
Again, not really sure about the full spectrum of things that it might cover as I only work on online content so that's mainly websites and services like online forms. I think any digital product would need UXD input at some point though.
Or if you were meaning what else do I do apart from digital design, it's things like creating and updating style guides/pattern libraries, presenting designs to teams across the organisation, and keeping up to date records of design decisions. The last one is so that if someone asks why something is a certain way, I can point them to the exact reason. This is very helpful when someone makes a suggestion and I know that we have already done that and it didn't work! 
Sorry that was so long but hope you found it useful. It's a great area to work in and I would recommend it to anyone.
And loving the suggestions for places I should get a job.
My dream companies to work for would be IKEA or Lego (if anyone is reading...!) - I'm all about that Scandi lifestyle!