nice one Barge, veneer looks great. How much width you got to play with ?
I'd probably clamp the veneer down to a nice flat surface with a straight edge and cut a straight edge with a sharp blade. You got to be super careful when you clamp the veneer down it doesn't crack it. Good luck ! Hopefully you got a few mm excess. Mark up the cut lines before and make sure you can bookmatch them.
EDIT: Before you do all this I'd cut the lengths you require. Less chance of the veneer cracking/snapping while you do all this. Press firmly down with a sharp blade. I do this on my mdf bench top so not worried about the cut marks
