Hi Mick,
Unfortunately, my memories are those of an 8 to 11 year old, and I had no idea at the time what I was looking at. So I must have seen loads of WD's for example, but didn't know them as such - just dirty black engines. Similarly with DMU's, they were all green turning to blue when I travelled on them, but whether they were Met Cam's or Cravens, I can't recall. I've only worked out that the legendary "Green" engine was probably a Jubilee from talking to the likes of Mick Nich, though that fits in with my rather vague memory of what I saw.
We saw a lot of freight going onto/coming off the docks, interspersed with DMU's on the Withernsea branch. One thing I do remember of that area, were the piles of wood all the way from the footbridge, back to Southcoates Lane bridge. The area between the docks line and the Withernsea branch was full of neat piles of it. I guess these were pit props (?). I can also remember looking off Southcoates Lane bridge back towards the city (i.e. looking West), seeing lots of wagons loaded with said wood.
Moving onto Marfleet, I used to sit on the concrete up and over steps at the West end of the platform near the signal box. This was down a short path from the truncated remains of the level crossing road, which had been replaced by a bridge - pre war I think(?). (I have a great photo of an A5 - 69837 stopped at Marfleet on a passenger, showing 3 small boys (one of whom is a dead ringer for the younger me!) on said steps - unfortunately it must have been taken prior to Dec 1958, when the loco was withdrawn, long before I went near the place!) I do remember occassionally seeing the pick up goods at Marfleet - seem to think the loco was something small like an Ivatt 2-6-0 possibly.
Stopped going by 1965 as the Withernsea branch had closed, and as I ended up at what Mick Nich calls the posh school round the corner from Botanic, there was much more to see over there.
Will follow this thread with great interest as the contributions of others fills in many gaps in my knowledge, and look forward to meeting you somewhere. (I won't be at York as I was at Rochdale's show last weekend.) As Mick Nich would tell you, I am always interested to hear and learn as much about Hull's railways, even though I left there in 1977, and have now lived down here in Derbyshire much longer than I did in Hull.
All the best,
Kevin