Thanks so much for the answer
I have a follow up question...
I live in the UK, most/all my customers are in the UK.
That would suggest I should choose NameCheap's UK data centre [they have three, USA, Europe and the UK]
It is a whole $1 a month more expensive. Which is maybe not much, but it is a large part of the price.
BUT... if I understand your answer correctly - it maybe doesn't matter. Because Namecheap doesn't 'load anything' - so any advantage of having the UK data centre is mitigated by squarespace servers being [I guess] in the US?
So, would it make sense to just get the cheaper US Namecheap data centre option... as there is no real difference. I mean if it improved the customers experience by loading up quicker - I think the extra dollar a month would be worth it.
Thanks again for any help