As I stated before - En/Decoders should not be instantiated once for the whole run but on an event basis. Utility functions do not need to be methods of a class and thus can be placed in a utility namespace. Where is the necessity of a singleton utility class? Geometry managers etc. are implemented as singleton classes already.
While I definitely agree that we should have a common naming scheme, I think that the current one is getting a little out of hand - for me definitely EUTelGeometryTelescopeGeoDescription is a name which is way too long. I don't want to suggest that we change all the old names, but we don't have to introduce EUTelUtilityWhatever objects, just use the namespace utility and utility::EUTelWhatever makes it very clear that this is a utility class from EUTelescope. Stop using all the namespaces by default if you want to have this additional information present.