Seriously? I am assuming you have never used online shopping before then, I'll show you how it works.
1.) You go to the website, and put the product in your basket.
2.) You go through the checkout process.
3.) At the part requesting payment you use a credit card, (in my case a Halifax Clarity card that charges no fees for foreign transactions, and uses the inter-bank lending rate for the conversion)
4.) You wait for your parcel to be delivered to you door.
Obviously you need to make sure the retailer you chose from inside the EU ships to the UK, and there are lots and lots that do. A prime example of savings including shipping can be that of OCUK's owners, Caseking, you can often buy from them and pay about €9-12 shipping and the item can be considerably less that even if bought locally, especially if they have offers on.
Also just to make it 100% clear, if I pay €550 for something and the bank rate is £1:€1.12, I would get that product for £491.07, so I don't see what relevance the value has other than making it slightly cheaper or slightly more expensive, after all you'd only be using this method if local retailers are gouging the pricing, right?
So, are we clear now?