Zoopla Ltd and Digital Property Group (owners of Primelocation .com) merged in 2012. Zoopla .co.uk & primelocation .com may be considered 2 of the major online property portals in the UK in 2016.
According to Semrush, zoopla .co.uk is in the top 2 organic search competitors of primelocation .com with them ranking for 35.5K phrases in common in the top 100 results on google.co.uk. This to me is a gaping hole in the Google algorithm...
Both domains are registered to 'Zoopla Property Group Limited' without identical registration details and are not on the same IP address.
Zoopla .co.uk & primelocation .com may be considered to be 'Doorway pages' i.e. one of “multiple similar pages in user search results, where each result ends up taking the user to essentially the same destination.” See https://support.google.com/webmasters/answer/2721311?hl=en.
Other sites use the same Google Analytics ID as primelocation.com according to https://ewhois.com:
Other examples exist in other sectors too. In my opinion, Google should be noting mergers & acquisitions (by reading the papers!), and adjusting search results accordingly to stop the 'colonisation' of search results with 'doorway pages'.