The Expert will be specific knowledgeable people at the Department of Transport, Arrive Alive Communications, the Road Traffic Management Corporation or others who might have the expertise to answer the question.
One of the main reasons there is speculation that you don’t take old car seats, is that you don’t know if it has been in a previous accident and has any weak points which could compromise your child’s safety if he/she is in an accident. You need to ensure that there are no cracks or weak points in the car seat frame, and that the safety straps/belts are in good working order before you put child into it.
The reason for mattresses to be purchased is for hygiene reasons as we all sweat and “shed” skin cells when we sleep, and this is all collected in the mattress. Also, mattresses eventually wear out and the foam is not as firm as when it was new, so for comfort and physical well-being, it would be suggested that you purchase a new mattress for your baby unless the mattress you have been given is fairly new. I hope that this helps and please let us know if you have any other questions.
