Just as an example; when I got my PSP imported, the game and the unit came to about £200, and an extra £30 for shipping.
Import duties, VAT, admin charges etc stung me for £60.
They charge import duties and VAT for the whole lot (incl shipping). If it gets caught, I think you're looking at about £100 - £150 less than UK RRP. (but don't quote me on that)
The problem is the way duty works; it depends how they categorise your items as to what duty it attracts.
If it doesn't get stopped, well, you're laughing

Like you say, with the £ to $ rate, it's well worth looking into.
Have a read here:
http://www.out-law.com/page-6235