That was my thoughts Bozza. I've bought a fair bit of stuff from Amazon that gets shipped by other companies. You money goes to Amazon then Company X sends it to you and bills Amazon. You bank details aren't passed onto Company X (as far as I recall from my bank statements). The only think Company X knows is you use Amazon and where you live.
You can see Amazon items in stock ready for shipping. Just do your search as normal, and you may also need to select a category. If there are Amazon-sourced item, there should be another filter option on the left (after the Price filter), which reads "Shipping Option Any Shipping Option Can be shipped within one business day from Amazon.co.uk".
It doesn't completely separate Amaozon and 3rd party products, but it's better than nothing.