i have taken some poor advise and have added a 2mm veneer to the side of a door frame to bring the gaps down on the fire door that is fitted, it has know been flagged up by the customer as not being able to be signed off what are my options

Many thanks

For timber based fire doors. The usual method to reduce a perimeter gap between the edge of the door leaf and the reveal of the door frame rebate is as follows:

1) loosen the frame to wall fixings and pack behind the door frame jamb using timber wedges to achieve the required size gap. Then tighten the fixings and make good the fire-stopping at the frame to wall linear gap. 

OR

2) remove the lipping from the door leaf edge and fix a suitable new lipping of the correct thickness to achieve the required gap size and using the correct adhesive, usually Urea Formaldehyde based. Plane-in as necessary.

Just to add that accepted lipping thickness is usually 6mm minimum and 18mm maximum for FD30.

Be aware that method 2) would possibly void the product certifcation for the door.