The only problem with Stoney Creek is that it is directly against the light to Immingham, as can be Spurn point.
Brian, if you can get to the South bank I believe you can get onto the riverfront seaward of the IOT (just east of the East road entrance to Immingham dock) - I used to go there in the 80's/90's and 200mm will get most of the larger ships in the main channel, coasters heading upriver will be too far off.
Spurn is nearly always open except on larger spring tides when it can be breached - it does cost