I don't have any detailed information but I understand you can catch flounder in the Ouse up to Naburn lock, so presumably there will be some at Goole.
Cod have been recorded as far up as Broomfleet on big tides, which is a long way up river.
sorry this will not help much but i have a good mate who was pilot on the boats based there he fished round there a few times blanked nearly all the time not worth a visit he told me. but its up to you if you decide to go let me know how you got on
If best place and "Macro" don't Pair? How is Macro? If this is a mark then I will give it a go If I can get some pointers as to parking, bait, method. There must be something closer to Doncaster where you can fish from land than Immingham?
You may well catch some fish back of Macro 'Cod' but it is undoubtedly one of the nastiest s**th**s to ever blight the face of the earth! Why not try Hessle foreshore to the right of the bridge? Nice scenic view, fair flounder and eel fishing, some sole in summer, small whiting and very occasional codling in Autumn/Winter.
Leave Blacktoft to the Avocets, I reckon.