If you’re near Didsbury “30 minutes from Manchester” should get you on the edge of the Peak District quite easily. Park up in Macclesfield and either head east into the hills of the Peak District or west into Cheshire. Both have plenty of quiet lanes to keep you occupied, but 50 miles in the hills will feel very different to 50 miles on the flat.
Bollington, Pott Shrigley, Long Hill out of Whaley Bridge, Goyt Valley, then either up to Cat n Fiddle or head the other way up and over Pymm Chair to Lamaload reservoir and back up to the main Buxton-Macc road. Head over that and down into Wildboarclough and explore the quiet Staffordshire lanes before coming back round again to Macc. You can make the Staffordshire bit as long or as short as your legs require, but most of the B roads in the Staffordshire Moorlands are quiet with stunning views.
There’s some hilly terrain though. You might not want or need a full 50 miles if you’re new to road riding.