Hi Tony,
Thanks a million, that really helps. One last question, where do you justify your scoring as this is something I have heard been mentioned before.
Thanks,
Tom.
In this particular case, my guess is that the justification resided in "Grey Matter". 
I have never been asked in an audit to "validate" a risk matrix or a specific methodology for a risk ranking.
Some possible reasons -
(a) auditors do not have time to study the details of most risk assessments unless it is a famous one like cooking time/temperature. For random RA's, they need to see that there is, minimally, a stated, not patently illogical, reason for higher/lower risk rankings/decisions.
(b) auditors are well aware that the originators of the standard have often included "risk-based" to cover their *** , knowing full well that there are an infinity of "correct" answers, and that it is a perpetual PITA to new respondents.
© auditors know that many people make them up as they go along (= based on experience / OJT / Proprietary) and that it doesn't matter anyway due to (b)
A few official published examples of risk matrices do exist, often 5x5, and often including the magic word "subjective". i usually keep one of these as an emergency reserve JIC and mentally load the global get-out - "based on ".
Here is an auditory example analysing the existing "official" subjectivity relating to risk evaluation of foods/ingredients -
rf1 - High Risk Foods.pdf 150.98KB
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Rgds / Charles.C