Apart from differing part numbers whats the difference in CDIs between the L,N and R model. Would an earler cdi fit an R model and visa versa?

yes.....they are all the same

Oh.. Ok. I wonder why the changed the part number for this cdi from the earlier models. From what i have noticed a part number that ends in 780 has usually got changes specific to the R model and with it being electrical i thought there maybe timing issues.

Its prob just a small revision to the map, possibly due to emissions or some crap like that.

Though a small change in part no can also be due to things such as a change in supplier

Yep it may well be a small change and not really matter but just wondered if anyone knew what if anything was changed. Like you say it could be emmisions as thats one thing that was tightened down with that model.