I'm sorry for the profusion of mails on this issue, but I think it's kind of important.
Google reveals that the Museum Copyright Group in the UK had a presentation on museum copyright issues in 2003 by the "Peter Wienand, Partner and Head of Intellectual Property, Farrer &CO"
They were so kind to place their material online here:
http://www.mda.org.uk/mcopyg/event02.htm
He has some very interesting things to say about the issues we are interested. Let me quote some relevant sections:
2. What is the nature of a copyrighted work? * Works need to show originality, and/or skill and judgement * Many copyrights may exist in any work or in an archival file.
9. How can rights be enforced in the taking of photographs of archival material?
* This is difficult to do under copyright law * However, rights can be enforced under contract law
11. Are there any rights issue relating to facsimiles?
* This relates directly to whether there is any copyright protection afforded to photographs of art works. Although this has never been properly tested in the UK, there is probably enough skill and judgement in the photos of art works to afford them copyright protection in their own right
So, there we are...nobody knows what the law is in this situation is.