Any suggestions on a suitable format for storing the additional information. I've done a small amount of investigation and have seen a couple of altenatives:
amalgamate the data(1) so creator and contributor become, <full-name> (<user-name>), e.g. Christopher Smith (ChrisS)
or use qualifiers(2), creator, personal name (e.g. Christopher Smith); creator personal address (e.g. ChrisS)
or we do our own thing, creator, name & user (+ same for contributor)
(1)
http://web.resource.org/rss/1.0/modules/dc/
(2)
http://www.loc.gov/marc/dcqualif.html