100% your fault. No insurance liability for the parked car at all.
The law says that the person who parked the car can be responsible and charged under something like driving without due care and attention, but as far as insurance goes it's 100% your responsibility not to hit another vehicle. If you had to drive on the 'wrong' side of the road to do that, then you should've taken precautions like driving slower or getting someone to see you out. If the other driver is to blame, then they should've been moving slower to make sure that there was not another car coming round the corner before turning in.
As much as I despise bad parking, it's correct that it should never be the fault of an unattended and properly secured vehicle in the case of an accident.
In your case, I'd be having a quiet word with the person that parks there (it's almost always the same one, isn't it?!) or calling the police every day you see it parked there on the non-emergency number. Eventually, they'll get fed up and do something about it, and that applies for either party.