I'm still working through the UK rules, ( https://assets.publishing.service.gov.uk/media/6a60a03c47af6... ) but one of those is explicitly addressing that: no more than 1 such device is allowed per circuit. Also those are 3.5A each on our voltage.
> you can't wave this away with instructions
But apparently you can with legislation about instructions.
Edit: government safety investigation https://assets.publishing.service.gov.uk/media/6a32bfea0bea2...
Final edit: "61% of respondents support having one device per household circuit while 19% considered that only a single plug-in solar device should be permitted per premises citing alignment with 44 Engineering Recommendations G98 Issue 2 Amendment 1, impact on the network, old wiring in properties and the ability of consumers to correctly identify separate electrical circuits.
Government response: Having considered consultation responses and stakeholder feedback, the government's approach is to limit the deployment to one per power circuit, subject to corresponding changes to the G98. Some respondents suggested limiting the total capacity per dwelling to 800VA, but we think the evidence for doing this is weak considering most UK dwellings have a minimum of two power circuits"
-- i.e. they thought about it and the concerns got outvoted.
It's probably fine. There's a lot worse lurking in outdated UK installations. Then we get on to ring circuits, which the rest of the world disagrees with and also seem to be fine.
Wait, people in the UK actually follow those instructions?
In the US, even with a warning, you'd get regular home fires as people hooked one of these panels into every available outlet just because they can. I wish I were joking.