During the Battle of Britain, what AA defenses were available, and where?

Question

Regarding the Battle of Britain (1940 Jly 10 - Oct 31), I've never heard anything about the AA defenses on the ground. Surely they must have had some AA flak guns? What kind, how many, and where were they focused?

Wikipedia has this to say:

On 1 January 1938, the British air defences had only 180 anti-aircraft guns larger than 50 mm and most of these were the older 3-inch guns. This number increased to 341 by the September 1938 (Munich Crisis), to 540 in September 1939 (declaration of war), and to 1,140 during the Battle of Britain. Production continued until 1945, averaging 228 guns per month throughout the period.

(Emphasis mine.) This is talking about a 3.7-inch gun (94 mm), and it begins to answer the question. However, there are no citations for it. I would also like to know where those guns were concentrated. London? Airfields? Ports?

Answer 1

In the late 1930s, Britain organized the 1st Anti-Aircraft (AA) division. Armed with over 100 anti aircraft guns, it reported to the Fighter Command, and its mission was to defend London against air attack, which did during the Blitz, and at other times.

In the early 1940s, it was expanded to defend large parts of Southeast England.