I've received a reply about the process for opening up the records for those under 100 years old.
"Thank you for your email regarding haing a record opened.
As part of your 12-month subscription, you are able to take advantage of our free evidence of death checking service via an online form. You need to be signed in and complete a form to request an officially closed record to be opened. We have a dedicated evidence-checking team to review all requests. We aim to process all requests and send confirmation of the outcome within 10 working days, starting the day after being submitted.
You will need to conduct a search for that person on the site to find the record. This is likely to include the name and address within the register, date of birth and occupation, as well as household schedule numbers.
You need to prove that the individual listed in the records is deceased in order to submit your request to us and for that the record to be opened. We can only accept a copy of an official death certificate (issued by the General Register Office or overseas equivalent) so please ensure you have this documentation before proceeding.
The only suitable form of evidence is an official death certificate (files supported: .jpg, .png, .gif). If we do not receive this valid proof of death, we will be unable to proceed with a search.
If the death occurred abroad, then you will be required to scan and send a copy of the death certificate provided by that country.
This will need to be the equivalent of a GRO certificate in England & Wales therefore must be the fully certified information. A scanned copy is acceptable as opposed to the original and this must contain all required information.
You are welcome to provide additional information such as siblings, occupation, evacuee or any other relevant information that may help us to search the data.
You will also be required to provide your contact details in order that we can get in touch with you to confirm the status of your request and to request more information if required
Once an officially closed record has been opened up, it is available to view immediately."