From what I read, there was a manual telephone exchange in Stowey
from 1926, but this building was not built until 1930 when the first
automatic exchange was installed and in use by September of that
year. I assume this automatic exchange required mains electricity,
as it was only in the late 1920s that electricity came to Stowey. I
think the previous manual exchange operated using batteries, charged
with a small generator.
I don't know where the manual exchange was from 1926 to 1930.

1929 photo showing no building, but both telephone and
electricity poles abound!
However, even in 1930 it was only the eastern side of the current
building, with the hipped roof that was built. This can be seen in
the 1947 photo (just behind the timber building which I believe was
the old scout hut).

1947 photo showing only eastern section (hipped roof)
The second section was probably built in the 1950s due to the
increased telephone use in the area. This date is based on the style
of the roof in particular which was common to many of the rural
exchanges built in the 1950s, along with evidence from photos of
1947 when it was not there, and 1960s when it was!

1960s photo showing both sections
The telephone exchange was moved to Banneson road in 1978, and the
then vacant building became the local veterinary surgery in the
early 1980s.
I wonder if it was at that time that the front was amended with
changes to the windows and entrance door - I doubt the old exchange
building would have had that frontage.
The maps from 1840 and later show there was nothing on this site
before the telephone exchange, but in the early 1750 illustrative
map, it does look as if there was a small structure in this
vicinity, but I don't know what that was.

1840 tithe map (left)
1880 map (right)

1750 illustrative map