As I am home now I can let the photos tell the story. Because I am damned lazy like that. My horse battery deployed.
Smoke from my own cannon firing (I shot at the bridge but caused no damage) has drifted onto my troops which have reached the town and are now in line. However, the enemy is already in the buildings and have fired at my lead battalion, causing casualties (note the marker). The next shot would kill the brigade commmander, oh dear.
Here you can see that the leading battalion has retired shaken and belatedly formed skirmish order; the second battalion passed its morale test and has advanced in its place and the third bn moved to the right. (the accompanying gun battery has already moved out of shot to the East of town) The Brigade commander is dead, the horse is laying on his side. Luckily the next brigade of infantry is right up there and is moving to the East of the town. I considered the leading brigade to be completely expendable.
I had already decided to target the bridge with my artillery, although I did not know how effective it might be with 19th century cannonballs. Paul said there were no specific rules for this but that we would treat it as a wooden building. But before I got the chance to shoot Paul's next reinforcements arrived and began to cross.