Based on evidence we haven't seen, and wording we haven't seen in the SJPN/written charge, as regards whether it is worth challenging the double white lines charge, I would say about 7.2.
Do both charges arise from substantially set same set of facts, or do they relate to separate incidents?
On the face of it, absent some causal factor outside of your control, hitting a stationary object is pretty much a slam dunk for careless driving.
With 9 relevant points, any conviction for an endorseable offence is going to see you totting up to 12 points.
Upon totting up to 12 points requires the court to ban you for at least 6 months unless you can persuade them that such a ban would cause exceptional hardship - that is to say hardship beyond what most motorists would expect to suffer as a result of such a ban. However, there seems little point in looking into that as you have already told us that you are going to lose your licence.