Pull Cord Broken on Bathroom Wall Heater?

We have a bathroom wall heater - Winterwarm WWDF20 which is an old model and can't find any instruction on how to remove the cover so we can replace the broken pull cord. I can provide an image if that would help. Any assistance would e appreciated.
Felicity, June 2022


done
Manual here

https://toolmedia-res.cloudinary.com/image/upload/toolbank/downloads/DIMWWDF20E_User_Instructions.pdf


Fghi, June 2022