I've ordered stuff from the US but via a retailer that sends to the UK - Tackle Direct. I had to pay import duty and handling fees at the point of order, but then it all arrived fine, just like any other online order.
Cost-wise it works out about the same, certainly not cheaper than anything we can get in the UK, so I'd only do it again for stuff we can't get over here.
No experience of doing the import declaration and VAT/duty payments directly though.