Appreciate the replies gentlemen. Maybe I jumped in too soon asking for opinions.
The supplier and I have sorted the issue and a new gauge is to be forthcoming. The wrong dial/graphics were fitted to the correct other bits. The supplier/manufacturer is Caerbont, and they are one of the easiest and most reliable companies I have had the pleasure to deal with.
Update on Smiths 30degC - 100degC water temp gauge
Caerbont happily made good the incorrect face and sent me a new gauge. Calibration spacing is slightly different to original, but more accurate.
Full marks to them.