My 9year old daughter can’t get enough of these roller skating ladies from over there in th US, but now she wants the Moxi skates, omg !, $270 a pair, my only saving grace is they start at size 4 US and my girl is only a size 1 UK, so just getting out by the skin of my teeth, but still, I looked into it and online in the UK £299, this works out at over $400, did export and import tax go up suddenly ?,

Maybe.
Could be Trump's tariffs are having an effect on roller skates.
Could also just be the exchange rate if the manufacturer is in the U.S.
Companies tend to want to be paid in their home currency, so Euro's need to be exchanged for dollars.
Or it could be the retailer markup. If you see it at footwheels.com or whatever in the U.S., and in the UK they're available at Josh's Sporting Goods, it could just be different retailers have different prices.

Or it could be a combination of all of those factors.
Maybe Josh's Sporting Goods is buying them from footwheels.com, has to pay the exchange rate, has to pay the tariff, and has to add on to the price in order to pay someone to go to the bank to exchange euros for dollars, read the regulations and ensure compliance, and go pick up from the post office a shipment from the U.S., before being able to offer them to you for sale on UKAmazon.