Hi, glad you liked the photos.
Lightning photos are a bit tricky to capture, once you've seen it then you've missed it, the only way to really capture it is luck (I took well over 100, only 24 had lightning in seven of which are any good.) It does help if you have a huge-ass storm with lightning bolts every few seconds :-) and knowing the rough direction its coming from, big storms=lots of lightning.
As Tim said I was using iso 400, and 3 seconds per exposure, f number was f/6.3. In answer to Codprawn, lighning would overwelm (read overexpose) it if its bright enough (as seen in the second photo) This would also overexpose anything, ccd, cmos, film, (eyes) etc. Had I known the flash was going to be that bright, then I would have stopped down to F/8 or so as not to overexpose it :-p. In caves, astrophotography, ect where there is little or no light you would need a much longer shutter speed to get as much light to form an image, here you have millions of volts creating lots of very bright light in less than a second, that in the instance of the second photo is relativly close to the camera. An exposure of 10-30 seconds at this apature would have been too long as I was handheld, plus any subsequent flash would have added to the image and overexpose it, not to mention noise.
Hope that clears everything up, heres to the next storm... :-p