The timing chain on early JLR diesel engines are a known issue, and if the dealer has recommended replacing it because of the rattle then this is certainly work you should have carried out. If the chain fails then it is highly likely that the engine will be destroyed and will require complete replacement. Unlike timing belts, the timing chain should last the lifetime of the vehicle unless there is an issue, so it is not considered as a consumable part.

The terms of your warranty should explain if the timing chain is included, but we would expect it to be covered in this case. Regardless, the fact that you have only owned the vehicle for a few weeks means we would expect the dealer to cover the cost of the replacement. If they refuse to do so we would advise that you ask for a free repair or a replacement vehicle, as it has a significant fault and could be argued as not being fit for purpose or of satisfactory quality. The dealer may well resist, but given you have owned the car for such a short period and is warrantied, you should stand your ground.