Well, I think the place might be Ingress Abbey, Greenhithe . I looked at it early on in this GTP but couldn't find a fit so I ignored it. Revisited this evening with further searches.
Possibly the HMS Worcester, Thames Nautical Training College or Merchant Navy College?
You have it John. The Merchant Navy College, and before that the Thames Nautical Training College. Greenhithe. Or as known by most 'HMS Worcester.'
I was there during the change from the ship to the site ashore. Did night classes on the ship in the mess hall, and then for a term at the college ashore. I was in the first intake to use the accommodation block which was state of the art at the time. I was studying at the time for Home Trade Mate. The college catered for all those studying for the Officer grades across Deck, Eng, Elec and Comms.
Even at that time, and before it was even completed, the writing was on the wall that time had moved on. The ships bridge was never completed and the planetarium remained an empty room.