Thats irrelevant to whether your descriptive statistics mean what you claim they do. Either you used the statistics you did cynically, and anyone who didnt notice deserves it pointed out, or you did it credulously; in which case you deserve it pointed out.
Im going to assume it was credulous since I can't know what you were thinking, and im not in the habbit of calling random people liars.
Given that the vast majority of voters in the last UK general election didnt have an option they could have chosen to register their support for scottish independence, it isnt valid to use the proportion of those voters to measure the opinion towards the matter either way. Thats the case even in a "rough and ready" or "back of the envelope" way.
This is because those voters, who were not provided with such an option, couldnt provide a full spectrum of information about the question to which the option relates. It doesnt matter whose fault it is, or why they werent given such options. The brute fact of the matter is that they weren't.
Statistics, such as percentages, don't have any argumentative weight on their own. Maths is just a language that can be used to describe reality, fiction, or even to lie. As such, numbers need some form of context to be useful in forming opinions about the world. Its that context that gives, or fails to give, the numbers their real world meaning.
Statistics, to stretch the analogy, is just a dialect particularly suited to describing things like how many cats are indoor versus outdoor pets.
If we were polling on that matter and more than 90% of respondents were dog owners, who our researchers asked questions about whether their pet plays fetch, rather than whether it is an "indoor" or "outdoor" pet, then you need to exclude those responses before deriving statistics about indoor and outdoor cats.
Thats true even if 90% of those dog owners also had cats. If if they lacked sufficient options to provide information relevant to the question, then there's no basis to infer anything either way. We just don't know about those potential indoor or outdoor cat owners.
This is why presenting the aggregate percentages, as you did, is wildly misleading in the voting context that you yourself have aknowledged. The responses of the vast majority of voters in the 2019 general election of the UK simply don't give if firm information either way on their opinions about an issue they didnt have a range of options to respond to. We just don't know about those potential scottish independence supporters, sympathisers, detractors, cynics, etc...
All that said, I do agree with you that the question of UK wide opinions is an interesting one, and I don't consider it entirely irrelevant either. IIRC there has been some polling on the question, and the results might interest you. Google is your friend there.
Oh a final thought: a few years ago now I completed this free course to brush up on some rusty statistics skills. You only need to pay to access things like marked assessments: the info is available for free and is well explained.
The other bit behind the paywall are segments teaching the basics of using R to compute stastics like percentages, but also inferential stastics that allow you to ask questions like how related are two things. What I did was complete all the "theory" content for free and then did the "practical" stuff during the free trial there.
Anyway, what really got me about the course is how clearly they explained what the numbers really mean, in plain english. If youre in the habbit of using statistics to form your opinions (which I think is fantastic) then I'd highly recommend it as worth your time. It would certainly give you a stronger grasp of statistics than most MPs seem to have, even the high profile ones.