How are you defining 'accident'.
Many instances of manslaughter are 'accidents' no?
For the purposes of discussion, lets say the woman in the Chelsea tractor above hits you and kills you rather than misses. Better yet say it's somebody else, we are always a bit biased when it's ourselves we are considering.
What you appear to be positing is that if she misses that person, yes, she was a bit daft to think she could drive in those conditions and really didn't understand the capabilities of a 4x4 or the road conditions but had committed no actual offence. However, if she had hit them, she did commit an offence?
I can't get my head around that is all I'm saying. Her actions were the same in both circumstances, it is pure chance whether there is somebody down the hill behind her.
I wouldn't drive like that, you wouldn't, but we know better, she apparently doesn't. Regardless I can't see a law for ignorance alone working in practice.
For the manslaughter part, I'd need to look at further links of
@glasgowcyclist 's nature to be sure on this, but for now I understand it as where somebody commits an offence the consequence of which is somebody dying, but that death was not the intention (the distinction between manslaughter and murder). There would still have to be an offence committed (or perhaps a lower standard of willful negligence), but I am still not a lawyer and would need to check the specifics.
This is all however in my mind getting a bit off the topic of the original post. My opinion on him, is that he should have been locked up far before he actually did, anyone who has been convicted 6 or more times for using a phone is a total menace who cares nothing for anyone but themselves and one could say it was only a matter of time before he did kill somebody.
My distinction for what it is worth is that he deserves longer behind bars than the woman in the 4x4, but as has been pointed out already, we don't always get what we deserve and 'luck' has a part to play.
TLDR. 100 quid and 3 points for a 6th offence of phone use whilst driving is ridiculous. The tragic consequences of the 7th (or greater) offence were an 'accident' waiting to happen. It wouldn't have occurred had his licence been revoked on the second (or any subsequent) offence.
ETA: Reg posted his shorter reply before I finished waffling on manslaughter.