Are there any features of cookers that make them rodent resistant? Our gas cooker has started leaking gas. It is likely that it is because mice have been living in the cladding for a good few months and they have finally got around to chewing through a gas pipe.

I am now looking for a replacement but there seems to be no direct indication in any cooker specifications that suggest it would be rodent resistant. What features could I look for that would suggest the mice will not get in again.

There does seem to be some notes on the Amazon website that some cookers have some rodent-proofing feature (such as the Bush AG56D) but the wording is unclear.
The hose that supplies the gas is probably not part of the cooker itself, but a separate part which can be swapped by an armored one. 

Manufacturers don't have a rodent-resistant label, what you need to know is whether chewable materials are part of the construction. The best way to tell this is to lift the lid and look at the supply to the burners. Generally these will be metal, not materials like rubber or flexible plastics.