Transformer for 12v Oven to 240v...

Should be fine but a lot of extra work to make it safe to handle plus its somewhat overkill.

However the oven only draws 6-10 amps (depending on the model.)
I'd rather see you buy a supply already in a finger proof case.
Something along the lines of the 10 amp model here-
https://www.ebay.com.au/itm/100-240V-To-12V-1A-2A-3A-5A-10A-Power-Supply-Adapter-Transformer-Charger-New/111548882454?hash=item19f8d4de16:m:mq5PeElxQmqgIOsvat5e3mA

I have a battery charger which also has a dedicated 12v power supply maybe an option with a battery charger thrown in

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Hi Mark, first missile of the "barrage"...............

The product you instanced does not meet the Australianelectrical safety requirements. It is an offence to offer appliances for sale in Australia that do not meet these requirements.
It is clearly a power supply designed for mounting within computer or similar equipment and from a search I see that it comes from a large batch (1000 plus) of offered surplus manufacturing stock.

That is not to say that it would not serve your needs, but it has obvious safety inadequacies....... The 230v cable is not adequately secured and the 230v terminals are not adequately shielded against personal contact. Further, the 12v 'cigar socket' is certainly not capable of handling the rated 30A output, 10A at most. Even if you purchased this product you would need to attend to these matters.

My suggestion would be to get an old power supply from a computer and use that.

Have a look at this article here

I would also advise replace the ciggy plug and socket and using the Anderson connectors especially at 10A.

I run my modem/router and NAS drive from one of these when at home, in the van it just plugs into the 12V battery.

Have you tried a portable car fridge transformer? I have a Waeco fridge that comes with a transformer which is very handy for running a multitude of things that have cig plugs on 240v.

I love my Travel Buddy fridge one of the best purchases I've made for the back of the Troopy!