hi
i'm not sure if this is exactly what you're looking for but narrs are currently running training events to help people carry out amphibian and reptile surveys this spring. the training events include some identification work but most also include some fieldwork. you'd learn loads about how to see reptiles in the wild and, assuming the conditions are favourable, there's a pretty good chance you'd see something on the day also.
you could then sign up for the survey and practice your new skills while helping out as well.
here is a list of training events
http://www.narrs.org.uk/training2008.html give the ones closest to you a bell and find out if it's going to be of any use.
what ever you decide to do, good luck and we will look forward to seeing some of your pictures in the future.
tim