The HQ element hasn't changed much since the Second World War and was pretty static throughtout. Battalion size increased from around 650 men to 845 men from 1938 to 1945 with more officers in the companies and platoond making up a battalion. Typivally a battalion HQ (a battalion being made up of of four rifle companies plus support) -

Lt. Colonel - highest ranking officer and in charge of the Battalion Major - second in command to Lt. Col. Regimenral Sergeant-Major - highest ranking NCO, assists the two chaps above, and establishing HQ set up. Generally these three would have access to some field car, jeep, or universal carrier (in a few cases) There may be additional adjutants (Captain or Lieutenants) as well as a Padre (from the Royal Army Chaplains Dept.)

Signal Platoon Sub unit answerable to the Lt. Col. Responsiblr for communication between various levels of organisation (primarily between the HQ and Rifle Companies; as well as regimental command above the battalion) Signal Officer - typically a captain or major Sergeant - adjuctant to the signal officet 32 men and various transport (trucks, jeeps, motorcycles, bicycles)

Administrative platoon Sub unit designed to help with day to day things. Keep the men going with food, ammunition, petrol, clothes, everything a soldier may need. Typically lead by captain or major with sergeant to assist. Lot of variation in men to assist

Mortar platoon As it says these chaps looked after the larger calibre 3" mortars. Typically a Lt. With men to transport and fire 6 mortars

Carrier platoon Later in the war Universal (of Bren) carriers became commonplace in the British army. This platoon would have 3 carriers typically led by a Sergeant and two Corporals (one for each vehicle) with wireless communication in each vehicle. Number of these platoons varied from battalion to battalion

Anti tank platoon Large platoon equiped with usually 6 6pndr anti tank guns and vehicles to transport them. Usually lead by a captain

Pioneer or assualt section Lead by a Lt. or more usually a sergeant leading ten men. They dealt with explosives, anti mine duties, and occasionally flamethrower duties.

Rifle companies (4) Lead by a major, with a platoon sergeant assisting. Under him was a second in command captain, and four lieutenants (of WOIII sometimes) leading four platoons each of around 30 men. They would have lee enfields, sten guns, bren guns, vickers heavy machine guns, PIATs, smaller 2" mortars and such.

Hope this helps any questions feel free to ask!