G'day, David,
Remeber my question
http://www.askabiologist.org.uk/answers
p?id=13067
I took it the museum as you have suggested - here is the answer -
While we don’t have any ambergris specimens we do have a reasonable sponge collection and we are now able to say that both your specimens are sponges.
The smaller one that you retained is known as a 'glass sponge' (in photo)
The big one we cut in half (the smell nearly shut down Invaresk) and its internal structure matched perfectly dried sponges in the collection- also from Low Head.
We are happy to have a go at identifying any further specimens.
Regards, Simon.