Would something like this help?

https://uk.vwr.com/store/product/591406/handheld-uv-lamps

OK, so it's not cheap ... but it's the first one I found and I'm sure there are probably cheaper options available.

wow thanks for all the replies!

i'll try:-

- changing angle of the light

- using the makers image to identify where the decal is located

- black marker pen on reverse


if all that fails I'll change to o gauge!

thankfully in n gauge the small decals are largely unreadable from normal viewing, its just to give the impression... so at least if i get the wrong decals it won't matter too much!

cheers


tim