It seems I'm having a sh!tty run of luck at the minute

Got in the car the other evening after a heavy downpour and after about two miles of easy driving, the car started to misfire really aggressively under load. It didn't seem to matter how lightly I tethered the throttle, whether it was low revs or mid range, there was a massive misfire and the exhaust felt like it was gonna shoot straight out the back of the motor!
After 800 yards or so the 'engine management' light began to flash intermittently. I managed to crawl home at a snails pace and the car continued to misfire like a thingy all the way home!
Next day I drove over to a friend's garage to have the car scanned, it was relatively well behaved on the 10 mile journey it didn't really miss a beat and the idle wasn't lumpy at all! I started to think it could have been the damp from the heavy rain and that the engine bay hadn't heated up sufficiently to clear it out.
As soon as I got there, the scanner got plugged in and I took it for a drive to try and replicate the misfire so it would pick up a 'fault code'. I drove around for nearly an hour and the thingy just wouldn't misfire
So I left the garage with the diagnosis that it probably was coil packs and/or spark plugs, but had no choice but to drive away (I hate that feeling of knowing that something is probably wrong, but the car is taking the piss out of you and you're ultimately just waiting for it to fail).
Ten minutes into my return journey, the car started to jerk back and forth, like Jimmy Savile at Broadmoor. I just couldn't believe it. I was thinking just my luck

When I arrived home, sorry I should mention I barely made it home at this point, for fear of every time I touched the throttle the car started to go in 'spaz mode'. The idle was lumpy and 'hunting' all over the place and the 'engine management' light was flashing constantly.
Needless to say I've got my friend coming out today to fit a new set of coil packs and a new set of plugs. Hopefully problem will be resolved. I hate nothing more than having a poorly car