Amazon have accepted that I own the content and have said they would take this content down
If you have a clear written statement from them to that effect you could include it in any DMCA-based request to Google. However, taking it to Google probably isn't the best approach, unless - Google Images aside - Google-hosted pages display your content. In general Google are pretty quick to address and remove infringing material on their own servers, but their line on disputes between third parties - you and Amazon - is that they are not an arbiter. As a further caveat, their primary interest is in their own position - not yours or Amazon's - and if ownership of material is in dispute they would be more likely not to display it at all than to remove only Amazon's.
However, I would be inclined to chase Amazon a bit harder on fulfilling their undertaking to do something about it before taking it anywhere else. Keep asking politely rather than threaten, and keep in perspective that what is major to you will be trivial to them.
If you really can't get anywhere by negotiation, you probably don't need to go to a non-UK court for copyright infringement (DMCA is not the only appicable law), as the infringement is happening in the UK. Depending on the value and extent of your claim, you could consider the Intellectual Property Enterprise Court Small Claims Track (see [gov.uk
]). Bear in mind, however, that if a multi-million organisation wants to fight, they will argue - not necessarily succesfully - that the case should be heard in a court you can't afford to fight in.
If the IP infringement is of substantial financial value, however, I would advise you to speak to an intellectual property lawyer before escalating your claim.