actually two fixes -
The students all being enrolled at site level was fixed by using the latest 1.72+ code for enrol.php which has a couple of patches back ported from 1.8 since our download.
The units not being picked up was a case of wrong drivers
- we selected oci8 when we should have selected oci8po it seems. Only discovered by trial and error.Anyway, all working wonderfully now - thanks for the help Helen
Roger