Thanks to all who responded. We found a solution, buried in NUCON is a b it that tells CMS if it's to use OS-style or VSE-style SVC's and by finaglin g that bit at just the right time going in and out of our routines, we have tricked everybody involved - RPG, ISPF, DB2/UDB and DB2/VM - into cooperating.
On to the next brick wall!
