Update: Turns out this was a plugin after all. I used to have a screenshot plugin called Awesome Screenshot which has 420,000 users and makes no mention of the fact that it adds affiliate links into your search results. I had actually disabled the plugin a few days ago but for some reason it was still changing the search results. I have now uninstalled it and the issues have stopped. Seems a like a plugin Google needs to ban & I have reported it.
The screenshot below is from Google Chrome incognito mode with no plugins. It shows how Google has replaced the standard Shopping results with a set of Amazon Results.
The links don’t look like standard Amazon affiliate links so they must be some kind of partnership links.
This is an example link through to the product page.
I’ve never seen this before but it’s very good for Amazon no doubt.