Hi again
If your person of interest was born after 1917 but died before 1991 they should be unredacted. The register was used up to that date for NHS records.
If they have died after 1991 and their death has been identified by FindMyPast or the National Archives, they will be unredacted.
Proof of death has to be supplied for those born after 1917 but you will need a 1939 address to tie everything up at their end, this address is obviously something you don't have yet.
What area do you think your person may be in? you can do address searches and maybe find the hospital/institution that way
You will only see the FindMyPast interface at the National Archives so maybe not a specific trip to make