A good range of loco name and number plates, very reasonably priced, are available from Severn Mill Nameplates. The range includes most, if not all, of the classes for which there are kits. (Of course many of the earlier classes don't need numberplates, or only need them for certain locos - please do consult photos.) For some classes, for example class 1 (Sam Fay) every engine is catered for. Does anyone have a model of all six? Lucky you!
An alternative supplier is Guilplates who unfortunately don't have a website as such, so you will have to send off for their list by post or ask for it at one of the exhibitions they attend.