We will use off-specular reflectivity to probe the characteristic lateral length-scales in responsive polyelectrolyte brushes grown by surface-initiated ATRP from solid-liquid interfaces. Our first aim is to see if the spacing of the tethering points imprints a lateral correlation length onto the brush in the form of a blob size as is expected from theory. Our second aim is to follow up the observations of multilayer structures that give rise to Bragg peaks in specular reflectivity. The presence of the Bragg peak depends on the grafting density of the brush and the number of repeating layers can be tuned by varying the brush thickness. All the brushes we have studied display a high uptake of surfactant, suggestive of aggregate formation. The nature of the aggregates will determine the lateral correlation length within the brush, and we aim to determine this using off-specular scattering.