I hate to put a "hole" in your story, my friend Moley, but i must indeed question the validity of your "vision".
Now, i believe you believe you saw this soldier, and it was and still is vivid in your MIND. With that being said, i can PROVE that it was NOT a ghost of a soldier in the English civil war.
One simple statement that you mentioned, disproves the validity of the person being a true ghost of an English soldier in your whole story. You see, saluting was NOT a practice of soldiers during the English Civil war. That practice did not start until the colonial era of wartime. It was adopted by that era of soldiers, especially during the American revolution, to mimic the old knights who would have to "raise" their visor on their metal helmets, in order to look into each others eyes.
This action of putting the hand to the forehead and saluting was adopted in the 1700s, as a throw back to chivalry on the battle field, and was purely symbolic as no colonial soldiers wore knights helmets.
During the English civil war, the action of saluting, as you say the "ghost" you saw did right before he "disappeared", was not, or ever done, by any soldier involved on both sides of the English civil war.
We must only conclude that this was a ghost of a colonial soldier, pretending to be a soldier of the English civil war, OR a figment of your 9 year old imagination. Or perhaps this ghost had quite a sense of humor, and we are all the butt of his joke. . . .
And to that, i must salute him . . . .