Hello Paddy

X ray film are usable as Ortho film I made some of my flower image with such film , take a look at these : http://www.c-nze.com/pages/flowerspirit2.html

Depending on the film the sensibility will startt from 400 iso to 3200 iso. I know use agfa Currix wihici is a good 3200 iso film. The second thing to take care is that they are often layer on both face so when you develop them you'd better take care to avoid scratch. for this I use a plate of glass in my tray .

The flower image you saw was made with a kodak Xray film develop in ABC pyro 1+1+1+25 for 4 min. With Agfa I prefer to use Rodinal at 1+25 for 4 minutes.
These timing are for palladium/ platinunm printing (neg with 2.1 DR)

Hope this help