"What about customs duty and import VAT?"
We collect regular VAT at checkout — and in most cases, that's that, you need not worry about any further fees.
To be a little more specific:
For any order up to the value of £135.00, you will not have to deal with customs duty or import VAT.
For an order that has a value of more than £135.00, it is possible that you might have to pay customs duty or import VAT to Her Majesty's Revenue and Customs (HMRC) — but this would be unusual because, wherever possible, we package orders in separate shipments that have a value that is below this threshold.