I bought some wheels from the US last year.
Theres differnt rates of duty for different goods , import duty on wheels is 4.5% , but then there is VAT
I paid $400 for a set of 4 , and the duty was £66 pounds.
I think at the time the whole lot cost me bout £480 by time i got them home. (inc duty and shipping from US)
I could only find one one place in the UK which could supply the same wheels and they were about £650 delivered , so even with the duty and shipping from the US i saved around £170 !!
I used this duty calculator for an idea before i ordered
http://www.dutycalculator.com/new-import-duty-and-tax-calculation/