Real Time Trains website will help. Use advanced search and put in TOC code ZZ. Lot of Freight flow is from container ports like Felixstowe and Southampton. Obviously inland terminals at Wentloog near Cardiff, London Gateway, Leeds, Doncaster etc. Stone trains from the Mendip quarry’s at Whatley and Merehead. Intermodal trains up the West Coast Main Line from Daventry. Biomass trains Liverpool to Drax. Binliners from Runcorn and Northolt. Network Rail engineering trains from places like Crewe Basford Hall, Toton, Millerhill in Scotland, Carlisle, Tyne Yard, Tonbridge West Yard, Eastleigh etc. A lot of freight goes up the West Coast mainline, so try places like Stafford and Rugby. Reading West is another great place for freight. Peterborough sees lot of East Coast traffic. Just to get you started..
there’s probably few videos on YouTube from the likes of Freightliner that may show you some of their operations
