I cannot speak for LeatherZ but have been importing from the US for a decade for Jeeps and latterly the Zed.
It's luck of the draw if you get hit for import duty, but generally if the sender puts a nominal value on the package (and many will) or if it's sent by USPS (post office) then it escapes duty. Sent by Fed Ex or similar etc. you will get hit. Remember the duty is on the total costs of goods, US sales tax AND shipping
May I suggest a telephone not email order, so you can explain the import duty position :wink:
Delivery can be anything down to 24hours but expect less than a week door to door, although if the UK customs grab it don't be upset if it lays in a shed for 2 weeks. At 2:1 conversion these are the gambles.
Hope this helps