Intermittent juddering & flashing dash lights HELP

Hi everyone - newbie to the forum. Hope someone can help.

My Mrs has a 2001 Jimny (1328cc DOHC) and it's developed a bit of a fault and I wonder if anyone can shed any light on it.

It's a bit long-winded so apologies in advance for the length of my description but I'll try to keep it as short as possible.

Couple of months ago after a bit of stop start driving around town on a warm day the car started to judder and jump and shudder as she pulled into a supermarket car-park and pretty much all of the warning lights on the dash flashed on and off. She parked the car up and worried about damaging it by driving she called a recovery truck. The guy arrived and gave it a spin around the car park and everything seemed alright. It drove home with no problems.

I couldn't see any obvious problems so serviced the car and changed the spark plugs for some nice new ones. The old ones were probably the originals and when I took them out they were a nice dusty browny colour but looked ready to replace. The problem didn't appear again so we thought it was all sorted - plugs being the problem.

However, today (once again it's very warm) she took the car out to visit a friend. The journey is about 15 miles most of it on a dual-carriageway... so a pretty quick road. Near the end of the journey as she slowed through a more urban area the same problem occurred again - juddering and flashing warning lights. she managed to bunny-hop the car to her friends and left it for a couple of hours. No problem starting the car for the journey home but once again as she neared home and slowed after some quick(ish) driving it happened again.

Once again I've had a look and can't see anything obvious so I'm pretty stumped. I'm wondering if anyone has experienced the same problem? Could it be one or more of the following?

1. Something to do with a temperature sensor as the problem has happened on warm / hot days after lots of driving and when the car slows to urban speeds.
2. Ignition coil - sounds a bit misfirey to me maybe?
3. Camshaft sensor fault?
4. Crankshaft sensor fault?

Any help would be very, very much appreciated.

Cheers
Joe