I don't know of any photometrist that has been able to use the U filter successfully without having a large (at least 1M) scope and/or a back illuminated CCD. Many even have problems with the B filter.
If you, or anyone, is interested in variable star work you should join AVSON (Austral Variable Star Observer Network)
http://tech.groups.yahoo.com/group/AVSON/. I set this forum up a few years back as a meeting point and target information dissemination centre for all those interested in southern hemisphere variable star work. While there are less than 100 members they include just about anyone doing amateur astro science in this hemisphere.