it's just occured to me that i can use the piston ring to check bore wear!.
Yup, that's what I did with my 1.9TD... it occurred to me too, after getting debatable readings with a bore gauge (a lot of falafalling about)
However, you will need a new set of rings...
I wrote some of my ring gap figures down somewhere, think I can rememebr where they are, so till I dig them out, from memory, about 0.7 ~ 0.8 mm gap , one cylinder somewhat more than the others (No.3 or 4 maybe)