OK, its done!
I epoxied the chip just outside the ring, between the plastic ring cover and the rubber ring cover
The chip did have to be aligned correctly - it had to be parallel with the key shaft or it wouldn't work (but any rotation about its longer axis made no difference, it just had to be parallel)
Pictures below
Now I don't need to worry about getting another chipped key made - all my un-chipped spares now start the car
I am not worried about people stealing the car as I have arranged my own secret immobilisation system, which doesnt require >£500 if I loose a key!
1. Blue tack experiment inside ring perpendicular to key shaft - Does not start
2. Blue tack experiment inside ring parallel to key shaft - Does start
3. Blue tack experiment outside ring perpendicular to key shaft - Does not start
4. Blue tack experiment outside ring parallel to key shaft - Does start
And with plastic cover back on - does start
And with exterior rubber cover on as well - does start
5. And then plastic and rubber covers taken off and chip epoxied to outside of plastic cover, then when cured just pull rubber cover on
6. And finally, plastic and rubber covers with chip in between them simply clicked back on around the coil - Ta-Da!