I am sorry to hear of your disappointment and my apologies for the late reply.
Non-qualification appeals can be very hard to win sometimes. As you will know Kings admits on score order and the last person to get a place allocated in March had a score of 229. Whilst each case is considered individually by the panel and the numbers of qualified appellants should not make a difference, experience tends to suggest that these appeals may be harder to win when a school has had to turn away large numbers of qualified applicants. There is also variation from year to year and from school to school - you may simply have had the ill fortune to get a tough panel in a tough year for that particular school.
he has secure level 5 predictions in the SAT's for English, Maths and Science, was a member of Gifted and talented throughout Year 6, had strong support from the Head Teacher and class teacher at his primary school, has evidence of independant learning gaining certificates in IT and excellent school reports and testemonies showing that he exceeds in all areas of his school work.
This all sounds good but it is not unusual at all for Grammar school appellants to have 3 predicted 5s and the weight given to being Gifted and Talented may depend on the size and context of the school and which subjects were named. My guess (and it is just that - a guess) would be that the panel may not have felt that there was sufficient explanation for the low VR score or sufficiently strong evidence to address that specific area.
I would also like to know if actually this decision was made before we had even attended the appeal hearing and whether or not it was a complete and utter waste of time? The representative from the school had no questions for us in the appeal hearing and actually told us our presentation was excellent.
Kings' appeals were criticised by the Ombudsman a few years ago and they changed from appointing their own Independent Appeals Panels to using the County's legal services. My overall impression is that these panel members take their duties very seriously and would not have prejudged your case without hearing from you. It is not unusual for the school's representative not to ask questions. They presumably had no reason to question the validity of your evidence and it is the panel's task to evaluate that evidence.
Any advice on where we go from here would be gratefully accepted
There is nothing more you can do for this particular school for this particular year (unless as Etienne has said you are concerned about the actual conduct of the appeal as opposed to the decision). If you are within reach of any other Grammar schools it would be possible to apply and appeal again as each school manages its admissions separately so you can have as many "bites of the cherry" as you wish without the outcome of one non-qualification appeal affecting another.
It would be possible to apply again to Kings for Year 8 entry next year. This would mean a new test and most probably a new appeal even if he passes. You would need to evaluate your chances, but sometimes a year or more on as well as a pass there is solid evidence of progress at secondary level which may help. It has even been known for a non-selective school to write and support appeals for Grammar when they feel they cannot offer what the child needs.