Comrades, I'm deeply indebted to your sterling efforts and attention to my diva demands. I called into a local plumbing supplier for kitchen valve taps yesterday, not knowing they had bathroom/showers on display. I've found the answer to the parts replaceability issue referred to by my contractor. The link below shows an enclosure which allows any variety of doors and shower units to be fitted and replace in future if need be: http://www.bathroomsni.co.uk/neptune-showers-leak-free-shower-collection-249-p.asp