depends on what ecu your car has.
from what I have heard most vauxhall/opel/holden etc. actually use a GM (AC Delco) computer/ecu.
I have a GM ecu and I have used Datamaster for a while now and found it to be a very good scan tool and datalogger. I've always used it with a laptop but now that I have time to do a carputer I'm looking forward to incorporating it into the design.
you can get Datamaster is at ttspowersystems.com.
find out what computer/ecu you have and go from there. do you have an ALDL port under your dash?