Thanks Sanjoy.
I took a flyer on the items in question.
They arrived very promptly indeed. As luck would have it, they fit perfectly in the sidelight aperture on the headlamp, and the spade terminals are also spot on for connecting up
2 things to watch though:
- the factory lash-up sees a short extension running from the spade terminals on the lighting circuit to the original, flakey bulb holder, which has a combo of a bullet and captive spade terminal pair...doing away with this makes connection a doddle but means the cable run is about 8cm shorter (I'm going to make up short extensions with male & female spades, but you could probably just do without them I suppose)
- as Ali pointed out on another thread, you need to reverse the circuit to drive the LEDs (at least for the ones I bought), although use of the std spades as above makes this a formality (except unless you did what I did to test the bulbs and ended up shorting the circuit across the bulb end cap

... one 5A fuse later and all is well with the world!!)
So there we go. Another successful chapter...for a change.