Hello Ted.
Not tried this myself but here are a few thoughts.
You can get lightning triggers that are quick enough to fire the shutter when they detect lightning, but I think they are expensive.
If the storm is at night you could try lowest ISO, smallest aperture and have the shutter on B for long enough to catch a bolt.
Or do the same but with a ND filter to allow you to leave the shutter open for a long time. This could help with storms during the day. A cheaper alternative is welding glass.
Unfortunately (or fortunately, depending on your point of view) the UK does not have the violent thunderstorms seem in other parts of the world, so capturing a lightning bolt can be fairly hit and miss, I guess.
Dave