Yep, it bumps up the cost considerably.
What ever you buy in the states is + shipping + 4.5% duty + UK end handling fees + 20% VAT.
When I was importing stuff years ago, the exchange rate was over 2 bucks to a pound, duty on car parts was 3% and VAT 17.5%. It's a very different world now.
Shipping via FedEx on a box that big would be at least £150 on their International Priority service.