Depends what you mean by a catch.

If you have an accident, you out yourselfin their hands. They can influence where the repairs are done (e.g. a Land Rover dealer owned or nominated bodyshop), and in the case of non fault accidents they will inflate the claim from the third party insurers by encouraging injury claims and providing expensive credit hire cars.

We all pay for it with higher premiums.

The insurance companies themselves will often pass their insureds' non fault claims to their own claims management business of to a third party one that will pay a referral fee. They have claimed that the oncome from this helsp them keep premiums down, but as the profit ultimately comes out of the claims paid and they are all doing ot to each other, that is rubbish.

We have had a couple of non-fault claims where we have chosen to approach the third party insurer direct. The claims have been handled swiftly with hire cars provided at no risk to us and using our own choice of repairer where we requested it. Not surprisingly, they were of course overjoyed not to be dealing with a "claims manager".

My son used Fiat's partner claims management service when his car was rammed amidships by a car emerging from a side road. They were not especially good at keeping him informed, pestered him to claim for injury (he wasn't injured), appeared to drag out the claim and put him into an expensive credit hire car while it was being sorted, which always involves signing an agreement that you will pay for it if the claim is not met. That usually works out OK, but it adds worry.