If you want like a Haynes manual, you kind of need two manuals. One for the regular XC Barina/Corsa C and one for the TS Astra (aka G or Mk4). Reason is, the Haynes manual was pretty much written in the UK, where the 1.8 SRi wasn't that common an option and they pretty much focus just on the 1.4. TS Astra on the other hand, was more common to see the 1.8 engine.
Or there's a free option, kinda based on Opel's TIS (Tech Info System, a Windows based program for Opel service departments), here at
http://workshop-manuals.com/vauxhall/
It can be a PITA to navigate, but hey, it's free.
Also, if you ever need to look for part numbers as such (ie helps with ordering from Autovaux, something you may need to do at some point), check out this online version of the EPC (Electronic Parts Catalogue) here at
http://ecat24.com/opel/catalog/models/1/