Google might recognise the old address, as 21 Mill St. Valour Pl. is the name of the walkway up to the front doors, due to the monuments along it. So the address is recognised as 1 Valour Pl.
Directions from the 401 (Toronto) are as follows.
Take Exit 282 (RR-24 S, HWY-24 S, Hespeler Rd, Brantford)
Turn left onto HWY-24 (Hespeler Rd) Travel around 5600m. Keep right.
You'll come to the mother of all intersections, go straight (ish) through the intersection. Once through keep Left. The Tim Hortonís should be on your left.
Continue onto Ainslie St N; street becomes Ainslie St S. you'll travel under a train bridge, down a hill, and the road will split, keep Left, Right is oncoming traffic.
Travel through three sets of lights, and turn Left onto Main Street (there will be a Mr. Sub at the intersection of Anslie and Main St. Take your first right at the TD Canada Trust. You'll see the Armoury now, (big red brick building, next to the Bus Station) the road will curve left and the entrance to the parking lot is on the right, it's free on weekends.