some links that may be of interest:

Fen habitat management from the point of view of Invertebrate conservation
The Bat House project now built in Barnes Wetland centre
information about the old Willingham West Fen pumping station (north-west of Cambridge)
Environment Agency info on eels
DEFRA info on eels including links to the Anglian area management plan
some more eel info, about what they don't know, from a London Zoo event
Last of the Honeybees a channel4 programme available online