Hi Des
Suggest you download the elearn workshop manual for the 244 Ducato from the downloads section as the 244 model used the 2.3 engine as well & you could get a timing diagram for it & the complete replacement procedure in the 1032 procedures section of the elearn workshop manual.
Below link is how to download the elearn manual in the downloads section & how to extract the ISO from the rar file & burn it to CD. https://www.fiatforum.com/ducato/265039-need-help-downloaded-manual.html
A post on the belt replacement schedule for the 2.3 https://www.fiatforum.com/ducato/242401-2-3-jtd-timing-belt-replacement-schedule.html