As a general rule, if you pull out of a side road, and a third party strike you, you will be held at fault.
Whilst I note your mitigating circumstances, all the other driver has to say is that he swerved to avoid a child - you will say I didn;t see the child, to which the response would be ''you didn't see the other vehicle either''.
Equally, speed will not be a point to argue over - you say he was doing over 40mph, yet you did not see him until the point of impact - if you did not see him prior to that, how can you comment on his speed? This would indicate that you had in fact seen him BEFORE the impact occurred, and therefore should not have pulled out.
And the police only attend if there is an injury or the road is blocked (probably is allegation of drink drive), but rarely in any other case.
This will in all honesty be noted as your fault