In reply to summitjunkie:
As I understand it, it depends on the individual company. Some, such as Bergzeit, Alpinetrek (Bergfreunde) - just as examples- are registered in UK for VAT. Some manufacurers (Mammut for example) are as well. You can buy from them without incurring Customs Duties/ additional costs. They also offer free delivery above a certain amount. They may also have UK addresses for returns.
Otherwise, there is a maximum value of £135/Euro150 limit, above which additional Duty/charges apply.
That's the situation as I understand it; I'm no expert.
However, (bearing in mind the above), I've ordered stuff from companies in Germany and Sweden since Brexit with no problems. Delivery seems to take a little longer, but that's all.
Check the delivery conditions on the individual retailer's website.
Hope that helps.