George at ASDa, Florence and Fred in Tesco, or if you are a little more mature Bon Marche... not all their stuff is what your gran would wear they do some simple classics which are good if you are woman rather than girl shaped.
Dorothy Perkins do reasonably priced work wear too.
On line: Next, and Littlewoods have a few, also try the corporate wear sections of the big uniform suppliers I got some of my work suits from there and a lot of the pieces are fully wash-n-wear. Google Corporate wear for lots of options