Part of my post seems to have disappeared above (I have this issue a lot on here on mobile - one of the reasons/frustrations why I stopped posting as much!)
On another Oxford post it was stated that around 10% had AAA for LLB, 20% A*AA, remaining 70% higher again. I cannot ratify the source though which isn’t helpful. Oxford does consider GCSEs, LNAT and interview. But there’s a strong positive correlation between top scoring GCSE grades and top scoring A-level grades - yes, there’ll always be an outlier, however we are talking about probabilities here.
Regardless, to tell the OP to consider applying to Oxbridge/KCL etc with AAA and no LNAT is a non-starter anyway.