Welcome to the Q&A Forum

Hi Nick, They are using schema markup on their reviews (AggregateRating <a class="attribute-value">- http://schema.org/AggregateRating</a> This is why the ratings occur in SERPs. Have a read of this page http://support.google.com/webmasters/bin/answer.py?hl=en&answer=99170 and then research on from there. Good luck and private message me if you want to discuss more. Davinia