I know this area well.
Looking at your map, car park number 5 (Brindley Place, Canalside) is a large secure car park, and only a short walk to where the canal goes under Broad St. Probably only a 2 or 3 minute walk.
From the Middleway roundabout just drive down Broad St, turn left at Sheepcote St (there is traffic lights and a Novatel hotel on the corner) and the car park is on your right (hidden amongst the office blocks, you have to drive between the office blocks to get to it).
The other good one is number 25 (Broadway Plaza). This is just on the left as you drive up Ladywood Middleway and opposite a huge Tescos. Note it is only about 100 yards up that road so look out for it.
This is also a large secure car park, and the entrance goes off to the left underneath the Broadway Plaza complex (cinema, restaurants etc.)
But this is a bit further to walk to the canal at Broad St, but only about a 10 minute walk.