Thank you for your question.
The free register plate is a simple sheet that your fitter would cut to size and make a hole in for the stove pipe.
We also sell register plates with inspection hatches and pre-cut holes, you can find them here:
800 x 400mm - https://www.directstoves.com/800mm-x-400mm-register-plate-with-cut-out-access.html
1000 x 400mm - https://www.directstoves.com/1000mm-x-400mm-register-plate-with-cut-out-access.html
1250 x 600mm - https://www.directstoves.com/1250mm-x-600mm-register-plate-with-cut-out-access.html
Hope this helps?