Peter,
Operating on the basis of the information that you have provided. (Film speed set at 125 on the camera and metering and exposing as we have discussed). If the film were exposing as advertised in your system, then 1/125 second at F11 should have given you a net density (after subtracting FB+fog) of .10. However the densitometer test indicate that this occurred in the exposure that you made at F 5.6 and 1/125 second. This indicates that the film is exposing in your camera and the meter that you are using two stops slower then advertised. This would mean that the film is in fact exposing at EI 32. My question is did you manually set the exposures on the camera with the film speed set at 125?
This seems to be an excessive compensation from the mfg advertised speed, in my experience with Ilford. If I were you I would check the meter reading on this camera against your other camera in the same lighting conditions. (Gray card, evenly lit...lens set at infinity and card filling the frame.) If your two camera meters agree, then I would shoot the film at 32. I suspect you have a meter problem, but check against another meter.
If in fact you find that the two meters agree in the same conditions and the film speed is determined to be 32 in your system then the next step is to expose under the same conditions (gray card, evenly lit, camera film speed set at 32, lens set at infinity and card filling the frame) manually set your lens and shutter speed to three stops open from what the meter indicates. This will be a zone VIII exposure. I would shoot the entire roll at this exposure, cut the roll into three even lengths and develop one at 20 % less then recommended, one at 15% less then recommended, and one at 10% less then the recommended development time. Have the density read on those strips . The one that will give you a density of 1.10 over FB+ fog will be very near your development time for printing on grade 3. The one which will give you 1.20 over film base plus fog will print fairly well on grade two.
To answer your earlier question as to my reasoning on printing roll film negatives on grade three paper, the longer that you develop film the more grain becomes apparent. This is most apparent on roll film (small negatives where degree of enlargement is greatest). By reducing development on roll film, we reduce contrast but we also reduce grain. We compensate for the lower negative contrast by printing on a higher contrast paper because grain is not an issue on paper.