Hi Martjin,
Thank you for your response,
This is strange, I haven't tried this yet but I've used Google.nl and found competitors to the site in the example who are using the same setup with votes, but the only one I see that has both the ratings and the offers in their listing is using the regular reviews correctly (attached).
I can't see what they're doing that is out of the ordinary - I'm currently using the exact same schema data, but the only difference being I'm using JSON for the whole setup while they're using microdata for the ratings and JSON for the offers.
Can you spot anything on this example that's out of the ordinary?