Hi Chris
Antara. 2.2 TD FWD 2012
I have the same spec as you.
The Antara comes with 17" - 18" - 19" wheels.
A comparison of the actual diameters ( with tyres on ) they are all within about 1/4 inch of each other.
Vauxhall sells a full size steel rim ( "winter tyres" ) This is what I bought as a spare.
It is a 215 x 16 [ 6.5 J ]
Don't let the 16 inch put you off.
The profile of the tyres that fit the different rims brings the diameters to near enough the same.
The steel rim takes a 215 x 16 x 70 tyre.
Conveniently it fits straight into the well after you have removed the central part of the expanded polystyrene that is there at the moment.
You will need a Torx screwdriver to remove the central screw.
I made a simple clamp out of a piece of flat steel to hold mine down.
You will need a jack and a wheel brace.
This gives you a full sized spare for about £160
The steel rim cost me about £80 ( I got 10% discount )
Just a note - an alloy rim is wide by 20 mm or so.
This is just too wide to fit in the well and have the boot floor close.
Somebody here got an alloy as a spare and had to have the floor section raised.
For a spare - the steel rim is all you need.
Hope this helps.
Antara. 2.2 TD FWD 2012
I have the same spec as you.
I have written about this previously - but here is a shortened version

The Antara comes with 17" - 18" - 19" wheels.
A comparison of the actual diameters ( with tyres on ) they are all within about 1/4 inch of each other.
Vauxhall sells a full size steel rim ( "winter tyres" ) This is what I bought as a spare.
It is a 215 x 16 [ 6.5 J ]
Don't let the 16 inch put you off.
The profile of the tyres that fit the different rims brings the diameters to near enough the same.
The steel rim takes a 215 x 16 x 70 tyre.
Conveniently it fits straight into the well after you have removed the central part of the expanded polystyrene that is there at the moment.
You will need a Torx screwdriver to remove the central screw.
I made a simple clamp out of a piece of flat steel to hold mine down.
You will need a jack and a wheel brace.
This gives you a full sized spare for about £160
The steel rim cost me about £80 ( I got 10% discount )
Just a note - an alloy rim is wide by 20 mm or so.
This is just too wide to fit in the well and have the boot floor close.
Somebody here got an alloy as a spare and had to have the floor section raised.
For a spare - the steel rim is all you need.
Hope this helps.