So it is really one incident but the CPS have charged as two. Well, there's certain sense in that, but personally , I would advise him to plead guilty to dangerous driving only and not guilty to the aggravated criminal damage. Two reasons 1) while the offence is not just with intent to endanger life, but committing damage recklessly and being reckless as to whether life would be endangered, too, I think that the plea to the one is quite sufficient and is adequate for the court's purposes and the prosecution's 2) the plea of not guilty need not be an acquittal on that count . The prosecution would invite the judge to "leave it on the file, not to be proceeded with without leave of the court or the Court of Appeal". In theory, it could be revived but, obviously, it won't be. This satisfies all sides.
But it's not my case and the defendant must be guided by counsel.
As to sentence, well just so long (extremely unlikely indeed) as nobody pleads not guilty by reason of insanity (result: instant incarceration in a mental hospital; not good in this case, the terms being very strict); and I hope nobody is foolish enough to consider that here (!) the mental history is important and helpful. The Court will need to be satisfied that, with treatment, the defendant doesn't present a danger to the public. Some form of hospital order is therefore likely, that being established, and the case is taken out of the category of sentencing for someone who is not so suffering