S500 Electrical Issue

Mercedes » S-Class » 2000-2006
Problem Description

Having recently bought a lovely low miles S500 (2004) I notice that the number plate lights are on permanently. The elderly previous owner said the car had a new battery, which is probably why the original battery kept going flat because he rarely used it of late 

When I checked the spec it is supposed the have Keyless Go yet neither does it work nor are there any messages. It is as if the feature is not installed. 

No fuses are blown under the seat (although the layout looks completely different to the chart) and as far as I can tell everything else is working and it drives great.

 

Any ideas please ? I was thinking that there must be a connection between both issues - a control module ir common short ?

 

Help !!!