Thanx for all the replies. A + for Phonedawgz - he called it!
The coil was working enough to get me home; after the engine cooled, it wouldn't start at all.
I tried the coil from my broken, swapped out '86 2.5L - it looks the same & has the same connections - '85 & '86 2.5L coils are the same number in the parts catalogue as the '85 to '88 2.8L.
I was surprised the two engines used the same coil... and the Formula is purring again!
[This message has been edited by David Hambleton (edited 07-09-2014).]