You may have to review a few manuals but this may help a bit:
http://www.credaheating.co.uk/helpcentre/download-manuals.htm
Have you asked the previous owner? Landlord?
If there is only one switch on the wall, that should be enough to turn Check for cables that disappear into the wall. or wall plate.
There are one or two spares outfits that seem quite helpful if you contact them. They may even be able to identify your heaters from photos
http://www.storageheaters.com/creda-storage-heaters.htm
http://www.storageheater.co.uk/
acp
June 2017