. . . in reverse.
Manchester Piccadilly station to Romiley station. Part of the Steel Cotton Rail Trail, named for the steel and cotton mill workers who used this route on their few days off to escape the grimy pollution of their respective cities.
The walk follows the Ashton canal eastwards from Manchester Piccadilly to Ashton-Under-Lyne. The route then turns south on the Peak Forest canal as far as Romiley. The canal towpath is in good condition and, apart from a short section near Guide Bridge, wide enough for two or more to walk side-by-side. Morning break is planned for Clayton (3 miles, seats around a canal basin). Lunch break will be at the Portland Basin Museum (7 miles, free entry, refreshments and toilets).
The 8:15 Manchester train from Sheffield Midland station arrives in Manchester Piccadily at 9:32. This train is on the Hope Valley line, calling at Romiley at 9:11. The walk will start from platform 10, close to toilets.
Return trains from Romiley are hourly at six minutes past the hour.
The best ticket option seems to be (senior rail card discount applied) Sheffield to Romiley, open return £15:30; Romiley to Manchester Piccadilly on the 9:12 train (i.e. staying on the same train), single £2:90. If coming by car, you can park in Romiley and buy a single ticket for Romiley to Manchester.