The storm that stands out for me in this area was the storm of May 28th 1999.
I remember seeing the BBC forecast earlier in the evening when they showed the lightning map (remember that?). I remember thinking 'What the hell is brewing there?' Around 9pm I noticed frequent flashes to the south moving slowly towards my direction. While standing on the front doorstep, the storm approached with a huge CB looking like it was on fire with constant red glowing and streaks of fork lightning jumping between the cloud. I kept watching for about 10 minutes until a bolt landed about 200 yards away. This was a point at which I knew this storm was extreme and it would be too dangerous to be outside.
As I wandered back inside the electricity went out, but it didn't go dark due to the constant flashing of the lightning. The strikes were now around 3 per second and the rain was coming down in sheets. The thunder was constant. This lasted for about 20 minutes. By the time it cleared the road was a river.
Looking back I think this was a supercell as I had never witnessed anything like it before or anything since