Different countries definitely have different market focuses. While some markets thrive on eBay I've found that it's pointless for me (in The Netherlands) to put my LEGO sets up there. Even if I'm the cheapest seller, and have a positive rating, people won't buy from me there. Dutch buyers hardly use eBay at all, and shipping abroad adds to the costs.
I have much better luck selling globally on Bricklink. I've sold LEGO sets to USA, Canada, Australia, Russia, Italy, France, UK... All sales went smoothly with happy customers and only good ratings received. Of course, buying on Bricklink is a higher threshold for many potential buyers than more commonly known places like eBay or Facebook Marketplace or other listing marketplaces. The downside is that you need to compete on price to stand a chance to sell, but the positive side to that is the buyers are by far majority seriously looking to buy a certain set and not out to scam you. Until now I've only had one 'buyer' making an order and not following up anymore about shipping preference and paying the invoice, which only resulted in a cancelled order and a negative feedback on their account. No negative consequences for me there.
Regarding British buyers buying from the UK mostly is probably true. A British buyer on Bricklink is a rarity for me, and after Brexit gets effective completely end of this year, they'll have to add import taxes as well when importing from the EU which will further diminish LEGO sales to the UK.
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On topic of 10251 Brick Bank ... on the local Dutch Marketplace the asking price for a NISB set is now ~ €285 and I see offers of €260 with one outlier offer of €290. I see it pass the €300 mark in the coming months.