Take a look at M.&.S. Outlet which is also online. They have menswear and suits. One point to remember is if you order on the Outlet, the goods come from Amazon so, unlike getting post from Marks you will not receive a prepaid postage sticker to return the item if you don't like it, you have to pay to return it.
The stuff on the Outlet changes all the time, as M.&.S. offload older stock, so worth dipping in and out every week or two.