CBC test results: Elevated MCHC, elevated MCH, bottom of range for Haematocrit, everything else within normal ranges. What do these results mean?

Nothing. Your physician may want to repeat them. I trust you do not have spherocytosis or if you do, that you've been worked up. At most, a reticulocye count may be in order. Sometimes the machines can be a bit mis-calibrated. High MCHC is quite uncommon and if you feel well I wouldn't be troubled. Reference ranges are set so that a few percent of healthies fall outside on either end.