Seeing as mods removed the necro post, I thought I'd shed more light on importing from the USA to UK. Lets take for example the Intel i5 3570kNewegg
has this for $219.99 with free delivery (At the current exchange rate this is £136.19)Amazon UK
has this for £162.74 with free delivery
Most people order a few items and dropship these in 1 go to offset their dropshippers delivery costs but these vary depending on the package weight but for the sake of it, say we are ordering just this CPU. Newegg will ship this free to your dropshipper in the USA. Your dropshipper with then forward this to you in the UK for about $40. So your cost has now risen to $259.99 or £160.95.
Now onto customs charges. The commodity codes for most computer parts means you pay 0 customs duty but if you import anything worth over the value of ~$24/£15, you have to pay VAT at 20%. So that processor you originally thought was cheap at £136.19 and then £160.95 (customs value) after your shipping costs will be subject to 20% VAT (£32.19) which brings your total cost to £193.14. Finally in the UK, it's mainly Parcelforce who handle getting imported items from customs to consumers. They will add £13.50 as their 'clearance fee' so after all charges, your total landed cost will be £206.64.
Now if you're unfortunate enough and find your CPU is faulty, you will have to ship this back to the USA and cover all costs again if you want it replaced. This doesn't phase some people but in the context of things with added local support and warranty, you're probably better off ordering locally because that sweet deal from over the pond may not look so sweet after factoring in all costs.