For me, the concept of border doesn't really exist. We live in different countries, but get along well with one another. I always work with models from everywhere (so-called abroad) and my customers also come from different countries.
At least within Europe everything felt very close and the borders weren't even noticeable. Plus, having the same currency, makes things really easy when traveling. Unfortunately, with Great Britain leaving the EU, this has changed. I am a little bit upset about it because it basically makes things difficult and I find that superfluous.
History repeating
It reminds me of how things changed with Russia in 2014. After relations between Russia and the EU got worse, this had an impact on my business, too. In previous years I sold calendars and books regularly to clients living in Russia. Through the political disputes however, the new exchange rates made my products super expensive for Russians. With the result that I lost most of my clients from Russia. It's a shame for me because I'm not political and my customers also just had fun with my pictures. The disputes were only happening on a political level, but still influenced my sales.
Brexit
Now, it's the same with Great Britain. A lot has changed due to Brexit. The pound / euro exchange rate has deteriorated for my customers. And in addition, there are hurdles when sending parcels to the UK. DHL shipping costs have doubled. They are at Swiss level now and on top you have the hassle with customs formalities.
That means, when shipping to the UK, value added tax gets added on import as well as a customs duty at a certain amount. Finding out details about this in advance is not always easy and questions remain, e.g. on how to declare goods.
You can get more information on this UK government website.
Additional costs
To sum things up, 20% VAT gets added to the price you paid to me (including the shipping costs, unfortunately) and you will have to pay a customs fee of 2.5% for goods worth more than 135 £ in total. You will receive a card from customs saying you need to pay this fee before they'll send on the package.
Example
You order a print for 100 € plus 26.90 € shipping. The total is 126.90 €. Currently this equals 111 £. After adding 20% VAT, the amount is 133.20 £ and luckily below the 135 £ limit. So, no additional customs fee applies.