Welcome back, Viv.
Just this last day or two I was thinking that we hadn't heard from you for a while ........
In the light of your circumstances, don't worry about the OoS. It appears to me that the headteacher thought that the format of the 11+ would not suit your son, and quite rightly predicted a score of 111-120. He/she might even have felt under pressure not to produce an over-optimistic OoS and thereby lose credibility! (If it's a very accurate OoS in percentage terms, you could turn this to your advantage, i.e. support from a very credible head!)
Despite the "3", the HT is
supporting your appeal for grammar school (at least I hope that is what the "very positive comments" amount to). It is certainly an issue that you will have to confront head-on, and as I haven't seen exactly what has been written, you need to be satisfied that this is a correct interpretation.
CATs are of course standardised nationally
(not for Bucks), and the 90th percentile is probably recognised as a good indicator for grammar school. However, the 11+ is carried out under much more stressful conditions, so a standardised CAT score in the mid-120s might well be preferred by panel members.
Under "normal" circumstances, therefore, the 103 would be unacceptable (and the most important score as VR is the measurement used by Bucks), the 119 would be regarded as very borderline, and the 125 as very acceptable.
I see no harm in saying that, according to NFER, 119 = the top 10% nationally
, and 125 the top 5%. (Best not to say "GL Assessment", as the panel are more likely to recognise "NFER"! Have a print-out with these figures from the website in case anyone has a query, but I doubt this will happen.)
The point you have to get across is that the range of CAT scores, from 103 to 119 to 125, and the range of KS2 predictions, from 4 to 5 and 5, is indicative of the problem with visual memory and motor skills.
You then need to go on and highlight all the useful evidence in the EP report. I would read out the bits that really help your case at the hearing. To make it easier for the panel to follow where you are referring to, say "If you turn to page 3, I thought section such-and-such might be of interest ......"
Don't get your hopes up too high, because obviously the outcome of any appeal is always uncertain - but it is very helpful indeed to have the EP confirming high cognitive skills (percentiles in the 90s). Even when the outcome is not the one hoped for, parents often tell me that it was money well spent (albeit rather a lot!) because they learned some useful things about their child!
You have permission to PM me if I can be of any further help.