The solution I found for this involved finding and downloading the relevant package on ctan. I had previously had trouble extracting the .dtx and .ins type files that are distributed with. The problem it seems was that my latex distribution is in "c:\program files" and the spaces cause problems.
I could imagine other people will have had this problem so in the more general case of updating a package manually under windows, try:
1) put your install file/files in a folder directly under c:\
latex <package>.idx or latex
3) copy the generated .sty files out of the folder and either put them in the relevant folder in the latex installation. (which I gather is bad practice) or in:
C:\Documents and Settings\<user name>\Application Data\MiKTeX\<version>\<package name>\
Though I haven't verified that the second choice will work.
I realise that I have actually answered a different question here, and it's slightly cack handed. It might be able to help some though and hopefully I can edit this answer if more experienced users are at odds with what I've said.