Hi, Having been in the same boat as has many others, ie incorrect name of my father, and I presume the myself, sister and mother, I contacted FindMyPast to be informed that I could use the option in the R/H corner of the preview page 'update the record' in order to amend said name, but this only gives options to open/close records or enquire about living people, no amendment choice at all.
The other thing that I have found is information about events that happened much later is included, my mother remarried in 1956 after my fathers death 1953, her new married name is shown in the index with her maiden name shown as being that of my father, I asked FindMyPast about that and I have been told that this register has been with the NHS until 1991 until it relinquished it, and in their hands hundreds of thousands of names have been amended, and presumabley other info as well.
I have found that it is more fruitful to search the road/street, if you know it, that way the whole neighbourhood appears, but again it is not much help if the name is not as it should be.
I think FindMyPast are doing a disservice to their paying customers, not to include in their many blurbs about the '1939 Register', the fact that it also contains information that has been added in later years and that this could cause issues when researching it.