Found a small rattle behind the glove box.
Bulb Holder? (There is also one under the drivers side). Strangely, there is no bulb ineither & I wonder why. From the "Burn" mark it could be a bigger bulb but with a wedge fitting (194?). Clearly something had been there before. Do Blazers come with lighting for the floor?

 

Yea my blazer is all lit up in the footwells under the dash. Those are the bulb holders as you figured out. The little clip on the underside is where the screw goes through to hold it in place.

I was about to type 'theres one on the drivers side by the OBD port'...but...with your RHD...my footwell is your glove box area! Wild... And mine has a matching burn mark, but I figure its ok since it burned all the troublesome plastic out of the way for me, it fits nicely now

 

What sort of bulb should be there? There's none in the holders.

 

It was a smaller bulb...looked like 194 if I remember right...but if no one else knows ill go pop mine out when I get home and letcha know!

 

Thanks mate.