Some useful links:

Gardening organisations:-
NGS: http://www.ngs.org.uk/
RHS: http://www.rhs.org.uk/

Events list:-
Wherecanwego: http://www.wherecanwego.com/
Open Gardens: www.opengardens.co.uk/

Education:-
Pershore college: http://www.warwickshire.ac.uk/
Winterbourne House: http://www.winterbourne.org.uk/

Speakers:
Christine Walkden: www.christinewalkden.com
Chris Beardshaw: www.chrisbeardshaw.com