Hi Gruntie, I agree on the brightness aspect, it's only a bench test at the moment and I did not have the filter on, that will probably make a lot of difference, ( I couldn't put my hands on it just then!) The only problem with the LED's are they are very directional and give a very bright light. Work in progress! but it certainly helps to be able to see the actual speedo needle!
With a spare speedo it's a lot easier to play about and experiment so I am sure I can get to the optimum visual delight!
Murray

It's a matter of opinion, but......I think you're going too bright. The speedo face is illuminated, you don't want that, the numerals should fluoresce on their own and just float in a sea of darkness.

A bit like the pic below: excuse it being a bit dark, crappy camera, but the speedo numerals are on a level with other illumination.

Just a quick photo of what I have cobbled up and bench testing.
5 UV LED's set in a 1/2 circle of plastic, certainly gives a good impression of what it might be like at the moment.

Thank you once again Andy ! That is very useful to know . When those LEDs arrive I have all the information I need to tackle the job !
I will keep you posted on progress and hope to post a photo of the end resul
Thanks also to Gruntie for his input.
Regards from the Emerald Isle ( wet & windy ! )
Pat

Yes Pat, the condition of the fluorescent paint will undoubtedly have deteriorated. I found there was a small improvement after I carefully cleaned the surface of the paint with isopropyl alcohol using an ear bud.

I also found that all the UV LEDs I tried needed to be mounted perpendicular to the black glass. They were highly directional - even the wide angle versions didn't throw much light (UV or visible) laterally, so mounting them in the orientation of the original tungsten lamp was no use at all.

Thanks for that Geoff, I see what you mean ! Compared to other bulbs on that site, this one is lowest in terms of " lumens " and the only one available in UV.
As you say, it may well be sufficient to cause the speedo markings to flouresce. i suppose to some extent it will also depend as to what degree the original fluorescent paint has degraded over the years ?
Pat