I would recommend a mirrorless body (Sony or m4/3) for the body for UV.
Unlike IR shooting, there are far less chances to find the UV-capable lenses in Nikon F mount or the ones that can be mounted on a F-mount bodies, unless you mostly do the closeups of the flowers for the bull's eye patterns or you can afford expensive UV Nikkor or Coastal ones.
If your main purpose for UV capture is the UV versions of your typical image making, you should have much more chances to find capable lenses in the older, single- or even non-coated L39 mount lenses which can only be mounted on the mirrorless bodies for normal shooting distances.