In the UK, the 16" SRi alloy was fitted to the C and I currently have them on my Combo (fitted with 195/45/16 as standard). Mine are (not by me) sprayed pink; they would normally be silver
The Opel Corsa D was only sold in Aus for a year, so a hard find for you, but those 4-studs fit fine. An ET40 (the C is 44) makes them stick out a little more, but looks good for it and has no handling drawbacks. I had some 16" facelift SRi wheels in repsrayed black with D-size 55 tyres which rubbed a little in certain circs (cheap lowering look!) but no real problems and fitting 45s would give no issues
I still have the C SXi std 15" with 185/55/15s (all weather tyres)
and, in Malaga, some Corsa D 15" (ET40 again) with summer tyres
Ordinarily, these would have 185/65/15s but the seller also had a C and they have correct 55s on them.
Tigra 17" Pentas will work, and 4-stud Meriva. This is an alloys catalogue listed on ebay that I keep a watch on. The last page might interest you. There are also Irmscher alloys that you can look up
It has a close up of a Zafira alloy on the front cover. Vectra C & Signum. Vauxhall Car Alloy wheels Brochure, 2004 Models with 4 pages dated December 2003, VM Ref No VM0304446. P2-3 show all of the then optional Vauxhall alloys for the following cars.
www.ebay.co.uk