If I am suspicious about a spelling of a surname, I check how many of tha spelling appear on free BMD. Precisely one Oslow (marriage in 1943) and if that one was pursued, I suspect it would be a mis-transcription.
Reminds me of several years ago, when I attended a U3A family history group. One of the members spent 4 months looking for an ancestor with an unpronounceable surname (not enough vowels). She had got this from a transcription on Ancestry, she continued this fruitless search even after I found the actual image of the register on FindMyPast, where it was clear it was a bad transcription of the marriage record and her ancestor's baptism could be found in a few minutes with the correct spelling.