Nigel,

I looked up Spendlove in the British Gunmakers Volume 2. There is not much information. Here is all that there is:

William J. Spendlove / Spenlove
Imkr, 11 (back of) St. Mary's Row
Birmingham circa 1926 - 1944
(different directories record the Number as 10 or 11
Probably 11 is correct)

Imkr means gun implement maker

Larry