Just had a quickish look through 'the Bible' and other references. All of the under side photos, the scale plans, wing construction schematics etc, show the circular inspection panels in these positions - no landing lamps shown or mentioned.
The wing was the standard 'E' wing (first production batch 'C' wing), and these particular panels were often doped, sometimes in the dull red used for the gun port patches, and sometimes they appear to be partly bare metal or primer.
I've worked in the past with two MkXIVs, the Rolls Royce owned 'high back' and the former Spencer Flack FRXIV low back (was G-FIRE, now in the USA), and I didn't see these lamps on either of those, nor on the BBMF's PR19s.
One particular under side shot, of Belgian Air Force machine, is very clear, and the inspection panel can be seen, painted as the rest of the under side.