Several occupants have left their marks indeed but it is difficult to tell which parts of the ghost signs go together. That's why I just put all I could decipher in one block
... / Shet... *
/: indicates successive ghost signs written at the same level
*: these two words are written diagonally with a completely different typeface from the rest.
The only occupant of 3 Great Hampton Street I have been able to trace was George Kelland, a milliner who certainly occupied the ground floor shop in 1878. Nothing about any of the businesses responsible for the ghost signs on the façade though.
Both buildings, which are grade II listed, are in a pretty sad state and if they were to remain empty for much longer, their long term future may be jeopardized.
Location: Great Hampton Street / Pictures taken in May 2012