Whenever I turn the electrics off, only the electrics as I've tried it with the engine on and off so it's nothing mechanical, It makes a strange quick pop sound? If I quickly turn the electrics on and off it doesn't happen, only if I leave them on for approximately 10-20 seconds. Has anyone else experienced this problem?

My guess would be a relay.
Try to determine exactly where the noise is. Perhaps stick your head under the bonnet while an assistant operates the key.