Hi, Tony

My thoughts ...

if you want to place your supply in a car ( and have fear of what COULD happen ) ... you should use regulators dedicated to automobile use, that are specially designed to whithstand the spikes and other funnies you can find on car 12v lines ...

ST ( between others ) has developped a whole line of such rugged regulators.

So just browse their catalogs, automotive applications sector ... and see what you can get from your dealer. ( Farnell, Mouser, Digikey ...)

or simply READ what manufacturers show into their Datasheets ...

Alain