No - please do not cut your hydrangea to the ground in August or late summer. This only stimulates late growth that will be damaged in the winter. Wait until early spring such as when you see the daffodils bloom to remove old, dead wood or faded flowers. Use your eyes to follow  the branch with the old bloom down to a point where you see a new bud. Cut just above this bud. If you must keep a pee gee hydrangea such as Pinky Winky in bounds remove entire branches and thin out branches that cross. You cannot keep this shrub small. You can train it into a tree form so that the trunk is bare with all of the width on top, but remember that like most hydrangeas, this shrub does great with no pruning at all - not what you wanted to hear as you are running out of room for yours. Perhaps you can move it to a new location where it can spread out - again wait until early spring to transplant this shrub and remember you get the best blooms from Pee Gee hydrangeas with at least 6 hours of full sun. Keep growing, Marianne Binetti