Managed to get this shot of a common green grasshopper while I was there though:
Nikon D700 + Nikkor 200mm f/4 Micro @ f/8, 1/4 sec, ISO 1600
For me this is an example of why the D700 is such a great camera for macro work. Taken just after sunset, at ISO 1600, the shutter speed used was 1/4 sec. There's a small amount of noise present, but on the whole it's still pretty clean image. This wouldn't have been possible with something like a D300. To keep the noise down to acceptable levels, a longer exposure time would have been needed, to the extent that there would have been very little chance of getting a sharp shot in the slight breeze.
Should find time to try again for glow worms later in the week. Apparently, the nearby Farthing Downs is also a good place to look, so that's my next destination.