Thinking along the same lines as Tecqboy, and knowing it was fine before the work, I finally got around to looking at the coil/distributor today.

On closer inspection I found that the HT lead at the distributor cap appeared to be a fraction higher than it should be. I took the lead off and tried to seat it down, but it still looked short, so I simply swapped it around to the coil.

Fired her up, and straight away she was back into a smooth idle, without any hesitation or stalling. Took a 5 minute drive up the road and it pulled like a champ again with no problems.

Hopefully problem solved...

Thanks to all!