I always use Tripadvisor
Whenever i travel business or pleasure i always check out Trip Advisor. As reviews are from actual guest they are for the most part reliable - However, you do need to read several reviews to make your own mind up. We recently saw one poor review amongst a lot of good ones and you could tell that the people leaving it clearly had their own agenda and it was simply untrue or embellished far beyond the actual problem. We booked the cottage regardless and the other reviews turned out to be true. Maybe trip advisor needs more moderation but it is very good regardless.