Am I rude?

[air3296]

I had a slightly awkward experience at the supermarket today and would genuinely like to hear what people in the UK think.
It was around lunchtime on a Saturday, and the supermarket was really busy, with quite a long queue for the self-checkouts.
The person in front of me had a fairly large shop. As they scanned their items, they took their time packing everything into bags, repeatedly hesitating and changing their mind about which items should go where.
I didn’t really mind that, as everyone has their own pace.
However, after scanning all their items, they still didn’t pay. Instead, they continued taking their time rearranging everything in their bags, while occupying the checkout and holding up the queue.
At that point, I said: “Could you please pay first? We’re in a rush.”
I wasn’t asking them to stop packing altogether. I just thought they could pay first and then move aside to finish packing, so the next person could use the checkout.
Now I’m wondering whether what I said was considered rude or impolite by British standards.
What’s the general etiquette at self-checkouts in the UK, especially when the supermarket is really busy? Was I being unreasonable, or was my request perfectly fair?
I’d genuinely appreciate honest opinions, even if you think I was in the wrong.

similar here, when I am more obviously disabled (eg wheelchair) it makes a small difference, mainly people treating me like I’m stupid but also being more thoughtful and giving space but when I’m not in a wheelchair it’s all bets off and every man / woman for themselves.
disability hate is real, especially invisible disability, it’s shocking hearing how people talk about it, especially those who definitely know better

To adjust your behaviour in the future, I'd suggest you avoid using the self-service check-outs and solely use the manned check-outs. Not only will you avoid situations like this, but you will also be helping to keep someone (at least a few people) in a job. And you'll also avoid the potential of offending someone when you feel they're taking too long.

The direction is which society is headed, will soon have that a real possibility, imo. Especially if a certain party gets in, next time around.

I find the self checkouts quite stressful and the thought that people are thinking that I’m being slow makes this even worse. I do think you were rude. Yes waiting can be annoying but that’s for you manage as a grown up. I’m not sure what saying something achieves other than potentially causing distress to the person you’re waiting for. A bit of patience goes a long way

If supermarkets are so stressful why not avoid them and get stuff delivered?

Not rude at all! These people need to learn.

Says the person making assumptions about random people on the internet 🙄

Need to learn what, exactly?

I don’t think you were rude but I might have insisted the staff who are always hovering, come move them along. I’m also one to ask a solo staff member manning a til with a long line if the could get another person to come open up another one.

Unless it's unlike any self checkout I've been at, paying first wouldn't change the time of you getting to use it.

You can't start scanning when they still have items on the scales.