James, further to my post above I have received this email from Tim Isles:
"I humbly beg to differ with your description of an original water temp gauge! I think your LM 5000 has a 30 - 110 gauge, but if you have a quick glance at Rinsey Mills' 'Original Ace and Cobra' you will see that all the Aces and Acecas are fitted with the 30 - 100 C gauge, with chaplets that match rev counter, speedo and all other minor instruments less the (Lucas) ammeter. Part number of the instrument is X20933/144 - I have one on my desk, freshly returned from SR, which comes from my Ace BEX 148.
I'm sure you'll know that three of these open chaplet minor dials (oil pressure, oil temp and water temp) are sold by among others Europa Spares and Speedy Cables, and appear to be known as the 'Cobra Range'. (SR do a very good job of converting the face on an early Sprite/Midget fuel gauge to the correct Ace pattern as it has the same shaped face and needle.) In my opinion these modern dials are a pretty close approximation of the original, but the detailing on the dials is a little more precise and slightly thinner. They also read 'Made in UK' rather than 'Made in England' which is an immediate give away that one is not looking at an original gauge. The big drawback is that the water gauge is identical to the oil temp gauge in the it reads from 30 - 140 and only differs in that it reads 'water'. I did have SR re-calibrate and re-face one of these new dials for me so that it reads 30 - 100. SR also mange to re-print the faces in the slightly 'fluffier' style of the originals."
Well there it is from the real authority - when I checked my water temperature gauges, including LM5000, they were all 30° - 100°C and of course, as Tim notes, the Lucas ammeter did not match the Smiths gauges.
Here is a Speedograph Richfield reproduction.