Largish low piston over Staffs?
 

Was in North Staffs on Sunday when I saw a largish piston a/c flying at maybe FL 030-050 West to East (I think), about 10-15 miles to the south of Congleton at around 3pm.

Any idea what aircraft it was and what it was doing? My initial thoughts were a WW2 aircraft en route to/from a flypast or the likes of Atlantic going back to CVT after oil spill mission in North Wales. It was too far away to easily identify the a/c but I reckon it might have had 4 engines and they definitely sounded like pistons.