Access to pipes

couple of drilled holes ( carefull of pipe locations) jig saw the amount you need out then, fit battens across to refix later, then if she is picky, get a square of white hardboard and fix that to the back, it will hide the cut out,

No matter what you do you'll be in for a bollicking anyway  
Put a big box of shit that nobody uses in front of the damage afterwards, that's worked for me!!

As Dickie said a hardboard back will pull out. Take the fixings out of the top rail, slide the panel up a bit to get it out of the bottom groove and it will bend enough to pull out. To make it easier to put back cut a small chamfer on the edges with a Stanley knife. If you have to cut it use the H trim battle suggested, or hardboard like tom said. 


If its a solid back use a multitool to cut it tight against the side panels. fixsome battens to the side panel to screw the back panel to. If you want to really go to town you can cut one side just right so that it will hinge out and still be big enough to slot half into the groove on both sides. this will hide the cut edges and be solid after putting  few screws in the top rail. 


Or just buy an access panel big enough for the hole you need to make.


www.screwfix.com/p/manthorpe-access-panel-white-243-x-193-x-16mm/20924?tc=ST2&ds_kid=92700038960972669&ds_rl=1241687&ds_rl=1245250&ds_rl=1249404&ds_rl=1245250&ds_rl=1249481&ds_rl=1249799&gclid=EAIaIQobChMI2b-kz-Tx4wIVhbTtCh1MtQQJEAYYBiABEgIMovD_BwE&gclsrc=aw.ds