It wouldn't have done what he wanted:
I want the neon to come on when the light is switched on.I wanted to replace the existing switch with this neon indicator switch to check if the loft light was left on.
Agreed, but I'd say spending five minutes fitting an indicator which glows when the loft light is off would have been simpler than rewiring to get a neutral to the switch. Although it was reversed, he'd still have an indicator that the loft light was on/off.
I'm not saying he's done anything wrong, just that he could have saved some effort.