The first RAF offensive sortie of World War II was made by 2 Group when Flg. Off. Andrew McPherson of 139 Sqdn. took off from RAF Wyton at 12.03. His Blenheim (N6215) flew over Schillig Roads where 75 photographs were taken of, apparently, "three or four capital ships, four or five cruisers and seven destroyers..". No Luftwaffe interception was made and the Blenheim landed at 16.50 hours.
20th September is the first mention I have of 2 Group being attacked by the Luftwaffe when three Bf 109s attacked a Blenheim of 139 Sqdn. but the Blenheim escaped into cloud.
21st September, Blenheim N6242 of 110 Sqdn. flown by Sqn. Ldr. Sabine was attacked by three Bf 109s. One was claimed by the air gunner, opening fire at 80 yards, the Blenheim then escaped into cloud.
25th September, Basil Embry flying P4857 from 107 Sqdn. was attacked by two Bf 109s and hit in the fuel tank, tail and turret but escaped.
26th September, Wg. Cdr. Cameron C.O of 110 Sqdn. was shot down over Kiel by Bf 109s.
For September, 1939, one bombing raid was made on 4th September against German shipping in Wilhelmshaven as primary and DDs in Jade River as secondary.
139, 110 and 107 Sqdn. took part in the mission which resulted in five aircraft losses and sixteen men, all to FlaK. While serious damage had been inflicted on cruiser Emden and three bomb strikes on Scheer.
I have a pretty good account of air combat between 2 Group Blenheims and Bf 110s;
10 January, 1940, Kenneth Doran leading a formation of Blenheims from 110 Sqdn. over the North Sea sighted five Bf 110s above them. The Blenheims were at 5000 feet in close vic.
The Blenheims dived to sea level, the Bf 110s attacked singly using cannon and machine-gun then breaking off in a stall turn at about 2000 feet for another attack.
One Bf 110 flew between leader and No.3 before breaking away, tracers were seen entering the plane. In the 25 minute engagement one Bf 110 was seen crashing into the sea, one Bf 110 was badly damaged and landed in Denmark while the remainder broke off the attack.
One Blenheim, L4859, had been damaged and fell behind the formation to be finished off by the fighters. It was seen crashing into the sea, this was the only Blenheim loss. One other was damaged and diverted to RAF Manby, while three others were damaged but returned to RAF Wattisham.
This was the first engagement between Bf 110s and Blenheims. It was found that the outer aircraft were the targets and it would be better to fly in boxes, rather than vics.
I will continue reading. There's more air combats between 2 Group and Luftwaffe. Mostly over the North Sea.
Early 1940, 2 Group continued with recon sorties but most were grounded or had to return because the weather was extremely icy. Operational sorties were flown on ten days in February, 1940. Heavy snow was encountered over the 2 Group bases and over the North Sea.
14th February, 21 Sqdn. carried out a reconnaissance of Borkum. The second Blenheim up (L8745) was called back, but never received the order. Heavy ice froze the aerials and the plane returned in darkness, Bomber Command disregarded the radio signals upon its return. Running low on fuel the Blenheim finally managed to touch down at RAF Tangmere when sighting Very lights at around 19.30 hours.
15th Feb, 21 Sqdn. sent a repeat of the previous days mission. Heavy icing was present once again. The second Blenheim (L9759) up was shot down over Heligoland by Bf 109s. Photo-recon was made by two Blenheims over Cuxhaven, Brunsbuttel, Heligoland and Wilhelmshaven.
Also on this day, twelve Blenheim crews began ferrying a dozen Blenheim Mk.Is to the Finnish Air Force. The crews were civilian clothing and were put in reserve, flying from Bicester the Blenheims were delivered with little trouble.
16th Feb, armed recon was flown by Sqn. Ldr. Doran to find and intercept troop ships heading for Norway. Ships flying Norweigan flags were discovered but they did not open fire on the Blenheim, because of the rules of engagement the Blenheim could not attack.
On the return flight Doran's Blenheim was intercepted by five Bf 109s, he was fired upon but managed to return. This flight proved the worth of the self-sealing fuel tank as bullets were removed from the fuel tank of Doran's Blenheim.
28th Feb, two 82 Sqdn. Blenheims fly recon over a Heligoland to spot any salvaging attempts being made by the Germans on a sunk British submarine. No attempt had been made to salvage the vessel.
4th March, 107 Sqdn. dispatch two Blenheims to reconnoitre flak ships and possible submarine salvage of HMS Starfish and Undine. Sgt. R.S Cunningham flying Blenheim N6183 descended below clouds over Schilling Roads to spot a U-boat sailing north.
Diving to 1000 feet Cunningham dropped four 250-lbs bombs across the U-boat, observing strikes on the conning tower. The U-boat was replaced by a wreck marker soon after, and Cunningham was awarded a possible kill.
11th March, Sqn. Ldr. Delap of 82 Sqdn. flew to Borkum for reconnaissance. When flying at 1000 feet he spotted a U-boat on which he dropped four bombs. The U-boat sank, this was confirmed by the oil patch that marked its spot. The explosions had twisted the Blenheims airframe and Sqn. Ldr. Delap had to struggle to keep his Blenheim airborne and get it home.
12th March, Sqd. Ldr. Sutcliffed observed German salvage attempts on the British submarines and attacked with minor results.
16th March, 21 Sqdn. dispatched nine Blenheims to attack flak ships. They were intercepted by Bf 109s over the North Sea. Two Blenheims were damaged but none were lost.
19th March, one 21 Sqdn. Blenheim and five 81 Sqdn. Blenheims went out to attack flak ships near the Frisians. The flight was intercepted by three Bf 109s but evaded them after entering sea fog. Moments later a lone Bf 110 also made a pass but was avoided by flying into the heavy fog.
27th March, eight 82 Sqdn. and seven 107 Sqdn. Blenheims attacked destroyers and flak ships near Borkum.
During the same time two 107 Sqdn. Blenheims were on a reconnaissance to Hornum and Lyst. Heavy anti-aircraft fire was encountered over Hornum but good photos were obtained. Fighters made an interception of both Blenheims, one was shot down.
I have no information on the French air force, sorry.