In November last year I was lucky enough to be at a research lecture run by Parkinson's UK. The main part of the evening was devoted to presentations by Dr Richard Wade-Martins (Oxford) and Dr Alan Whone (Bristol). They described some of the world leading work that they are doing including the GDNF trial.
The presentations were videoed and are now available to watch online.
http://www.parkinsons.org.uk/content/clinical-trials-and-parkinsons-what-does-it-take-find-cure
EF