[Kevan]

I hope you're only joking Graham...

Not 'modified' but standard chassis as supplied by Scalextric, doesn't come with the plastic hatch. 

   

The brass ballast is glued in the hole, it's not a working part of the chassis.

So before I go any further this obviously needs 100% clearing up please...is this Class A or not?

Rule reference:
General
G5) Ballast may be added but must be inside or as part of the chassis.