My daugther got 120 120 on her bucks 11+ tests.
Very good scores and you have very little to prove.
She was predicted to pass and her HT has given her a glowing report, with a 1:1.
That will count for a lot, provided the Head's recommendations are reliable overall. You will get that information in your appeal pack unless the Head is willing to share it with you beforehand.
However, being at an independant school, Key Stage tests are not carried out, although her HT feel that she is working towards level 5. Should I ask her HT at what level 5 she feels she will achieve?
The Head may enter it on to the form. Some prep schools still use SATs papers as school exams, so it is worth asking about.
Her NFER CATS scores were 121 in quantitive, 120 in non verbal, but she only got 112 in verbal. Is this worth mentioning?
Yes, her strengths do not particularly lie in VR, and therefore the Bucks test may not have allowed her to demonstrate her true ability.
Her familiarisation tests were fine too. (She passed all three)
Of marginal relevance, because the same papers are used every year and panels know that some children may have seen them before.
She has a reading age of 14 years months and a spelling age of 12 years.
A panel will look for 2 years above chronological age, so they are both fine.
You have strong HT support and provided that, her reports and her books show high ability your chances of success are statistically 75%, but with a 1:1 recommendation they may be even higher.
Please remember that the panel are looking first and foremost for ability
, and "hard-working" plays second fiddle to that. She is clearly both able and applies herself, but ability will always win.