I have done a little UV photography using Ilford HP4 and a UG 1 filter from Ealing Optical.

For landcapes the filter acts as a strong neutral density but the overall result does not look very different from normal except more hazy as you might expect.

A tungsten lamp using this filter on the lens enabled me to take a self portrait showing 'invisible' skin blotches and blemishes (quite scary). This is used in forensic photography to detect bruises after they appear to have healed.

The filter is quite expensive (it cost 50-60) and was used for a forensic project. I have never tried it with colour film.

I agree about the website mentioned above. Very good.