Hello Gill,
My starting point is Hull and I can't believe your luck with the Hull census giving you the info "Andreasburg"!
If you Google for Andreasburg, this shows it's now in a National Park and the civilian records are in Goslar. Then if you first Google for Osterode then 2nd look within that for Andreasburg, the only mention is a travel company with a "Destination" facility. Using this facility, Enter a start point of Osterode (Neidersachsen) and an end destination of Andreasburg. The latter has 3 mentions, one of which is also Neidersachsen. You will then be shown a map of the area which incorporates your chosen route.
Regards,
Rena in England