Roy
I think you have made a very sweeping statement and your assumption that the address was any thing other than a guest house may be quite wide of the mark. Of course, you have a person of interest whose history may make interesting reading. You don't say why he was considered undesirable.
A law student, a medical student, bank clerk, refugee and guest house proprietor could be typical residents of any address in parts of London close to universities and training hospitals.
You don't make the same assumption for the residents of 63 next door, where there is a similar mix of students.
I had a look at the electoral register for 1939 and many of the names eligible to vote were listed on the 1939 register.
There was a lot of xenophobia (dislike of or prejudice against people from other countries) which is why those who weren't born in the country anglicized their names, not only to make spelling easier, but for integration and acceptance in society.
If the property had a reputation for housing undesirables and threats to the nation, there may be files at the National Archives. Also try the London Metropolitan Archives and maybe newspaper reports.