Some years ago, prior to the decision of the Court of Appeal in Zurich v Umerji [2014] EWCA Civ 357 I published a paper on whether a failure to claim on a comprehensive insurance policy, and instead to utilise a credit hire car could constitute a failure to mitigate.
There has been (to my knowledge) no authoritative decision of the Court of Appeal on the point.
The paper can be downloaded here: Credithire barrister Comprehensive insurance courtesy cars and credit hire newsletter