Kiitos Essex2visuvesi for replying,
Sorry Mo, I didn't spot your mail.
Yes, the kitchen roll is thick adsorbent paper used for mopping up spills but it's laminated and the laminations are, in this case, punched together using a square dot punch roller that had EXACTLY the right pitch for the job. OK, I know that the holes on a grating should go right through, but who's counting?
I stuck it on cereal packet card with spray adhesive (trying to keep the design square), soaked it with very thin resin used for wood repairs and then painted it with a coat of acrylic wood varnish. Once that had dried, I used a very thin black wash of Warhammer paint which dropped into the 'holes' and that was it.
Tony