The Willenhall museum of locks looks interesting, but for first time visitors to the UK, the first stop should probably be the basement floor of the Science Museum in London (specifically the Secret Life of the Home) and on a more wrought-iron note, the 1st floor of the Victoria and Albert museum across the road. The Science museum has a library with some lock books also.
The websites are:
http://www.sciencemuseum.org.uk/
http://www.vam.ac.uk/
Both of these places have considerable holdings in locks. The science museum exhibits are better explained, but the V&A has some nice warded locks and padlocks. Both museums are free entry as far as I know.
The Bricard museum in Paris is also worth a visit.
http://www.paris.org/Musees/Serrurerie/
There are also a number of museums with locks in Germany and Austria. Perhaps one of the locals could tell us a bit about these?
Also - could someone who knows about it send in some info about the Mossman collection in New York. I'd love to see that museum
