I was 25 miles away so wasn't in a position to initially physically help her, but advised to try and re-start or 'bunny hop' it onto the pavement on the starter.
She rang back 10 mins. later to say she'd actually managed to get it going, and limped at 10mph into nearby Chester Zoo car park.
I rang the AA when I eventually got to her as it was indeed running very roughly, and in no way was going to be driven home.
Plugs and points checked, he turned his attention to the dissy cap, ignition leads and rotor arm, and suspected one of them.
Compression was fine which was my initial fear.
Only running on 2 cylinders, so dissy cap now the main suspect.....but.this was replaced only in January, and does indeed look new.
Magnifying glass didn't reveal any cracks however, so the mystery continued, and was duly towed home.
This morning, I found in a box of bits that came with the car, what looks like the original dissy cap, old and grubby, with matching equally grubby looking leads with original brass plug attachements!

Fired up, and perfect!!

Since been talking to a mechanic today that has a keen interest in old cars, and he tells me that plenty of dodgy poor quality spurious parts are now flooding the country, including distributor caps.
Anyone else had similar problems?