Academic Research:  
University of Bath Centre for Death and Society
University of Sheffield The Natural Burial Project
University of York Cemetery Research Group
University of Durham Dr Hannah Rumble - Natural Burial research paper.

Some useful links:  
Click here for a complete list of English Heritage Cemeteries.
  Also, in the Cemeteries and Crematoria search, each is marked with the English Heritage logo and its contact details may be found.
The independent voice of the funeral profession.
Info on crematoria in every EU member state.
The Bereavement Register
Institute of Civil Funerals
Society of Local Council Clerks
Local Government Association
Paradise Preserved

Anglican and Catholic Diocese contacts:  
England by diocese 

The United Diocese of Aberdeen & Orkney

The Church in Wales - Yr Eglwys yng Nghymru

Roman Catholic diosceses of Great Britain