Emma B

My fire door has just been inspected in high rise flats. There are a couple of gaps at the top and bottom of the door where a new lock has been fitted. Is there a type of fire resistant filler that I can use to rectify this, could I fill the gaps with an wood or would I need to repurchase the original lock and replace? I'm really looking for the cheapest option that would pass the next inspection. Also, would I need professional certification on any work that was carried out? Thanks!