Found an unknown species, whom should I contact?
Natural History Museum; UK, is a good resource. 

http://www.nhm.ac.uk/take-part/identify-nature.html


  According to their webpage;
  
  Have you found a strange bug or a new plant in your garden, or stumbled across an intriguing animal bone or fossil while out on a country walk? Let us help you find out about it. 
  
  Four ways to identify your specimens and sightings
  
  
  Check our selection of ID guides and apps below to see if one is relevant.
  Upload your photos and descriptions to our online identification forums for help from our scientists and other naturalists. Please tell us as much about your specimen as possible, including a detailed description, where and when you saw it, and its approximate size.
  Post your specimen or photographs to:
  Identification and Advisory Service
  Natural History Museum
  Cromwell Road
  London SW7 5BD
  Visit the Centre for UK Biodiversity at the Museum and show your wildlife or geology specimen to a member of our ID team. Drop in between 10.00-12.00 and 14.00-16.00:
  Monday to Friday (except bank holidays)
  the first Saturday of the month (or the second Saturday after a bank holiday weekend)
  If you need to discuss the best way for us to help with your enquiry, call our Identification and Advisory Service team on +44 (0)20 7942 5045 or email us.
  
  
  See more at: http://www.nhm.ac.uk/take-part/identify-nature.html#sthash.UGsoIYvE.dpuf
  
  


They also have provided some downloadable apps and pdf document resources in their webpage.