How to Service and Replace Cartridges in Franke Olympus S tap All aspects of plumbing questions and answers, help, tips and information

[ps11]

Hi
Having trouble dismantling a Franke Olympus 'S' tap in order to service/replace the cartridges (ceramic disc valves).
Here's the exploded diagram:
http://www.central-servicesuk.co.uk/shop/shopimages/olympus%20s-parts.jpg
I've managed to remove diagram parts #11 and #6 [grub screw and tap lever assembly], exposing the toothed end of the cartridge.
The component I'm having a problem with is #5 [the 'shroud' that surrounds the cartridge].
I've read elsewhere this part should unscrew - but mine doesn't seem to want to budge at all. It seems really stuck fast.
Can anyone confirm this part should definitely unscrew? If it should, then I suppose it must be stuck with a load of limescale that needs softening/removing with vinegar or something.
Any advice welcome.

P.S. I do have a photo but I'm not sure how to attach this to a post in this forum.

[ps11]

Having spoken to a very helpful person at Central Services, it's now confirmed this part does unscrew.
I ended up winding a piece of old bike inner tube around it and then using a wrench (inner tube to protect the chrome from scratching/denting). Worked a treat.
Also confirmed at the same time, the need to then undo the main nut head of the exposed cartridge end - will be doing this soon - cartridge should then loosen and come out ready for replacement.