MDL-47494 ddmarker: OU-2488 Proper British English

question/type/ddmarker/lang/en/qtype_ddmarker.php

@@ -66,7 +66,7 @@
 $string['shape'] = 'Shape';
 $string['shape_circle'] = 'Circle';
 $string['shape_circle_lowercase'] = 'circle';
-$string['shape_circle_coords'] = 'x,y;r (where x,y are the xy coordinates of the center of the circle and r is the radius)';
+$string['shape_circle_coords'] = 'x,y;r (where x,y are the xy coordinates of the centre of the circle and r is the radius)';
 $string['shape_rectangle'] = 'Rectangle';
 $string['shape_rectangle_lowercase'] = 'rectangle';
 $string['shape_rectangle_coords'] = 'x,y;w,h (where x,y are the xy coordinates of the top left corner of the rectangle and w and h are the width and height of the rectangle)';