Overall, the British Army was not as badly off as many think by the time the Germans were reaching the point they could actually execute SEELOEWE.
For example, 548 Cruiser Tanks had been built by 30 September; 158 had been lost in France and 137 were in Egypt, which still left possibly 250 in Britain, enough to equip the four Cruiser regiments of 1st Armoured Division that were active. The situation with Infantry Tanks was even brighter, of 524 completed, 126 (the Half-yearly RAC Reports give 186, but that appears to be an error) were lost in France and 52 had been shipped to Egypt on 18 August leaving about 340 available, enough to equip the five regiments of the GHQ Reserve 1st and 21st Army Tank Brigade to full War Establishment and leave enough left over to allow the continued training and equipping of the six regiments of 23rd and 24th Army Tank Brigades at about one-quarter establishment. And there were a plethora of Light Tanks available, of 1,340 built, 407 had been lost in France and 275 were in Egypt, leaving over 650, nearly enough in theory to equip the dozen or so regiments formed to War Establishment with a small shortfall. Note that by actual count the three ‘light’ regiments of 22nd Armoured Brigade averaged 42.33 tanks, 73 percent of their War Establishment of 58.
Just 139 A11 Infantry Tank ‘Matilda’ Mark I were built, 65 prewar and 74 between 1 September 1939 and 31 March 1940. In contrast just 2 prototype A12 Infantry Tank ‘Matilda’ Mark II had been completed prewar and 34 more up to 31 March 1940. All production Matilda from 1 April 1940 were A11 Mark II, but were supplemented by Valentine production beginning in May. There were a total of 121 Matilda II and Valentine ‘I’ tanks produced in the second quarter, 227 in the third and 354 in the fourth of 1940. Of the 140 Mark I, 97 (?) were lost in France, along with 29 (?) Mark II. In addition, 50 Mark II went to the desert in August 1940. So although the bulk on hand with troops as of 1 June were Mark I (60+), by the end of September the majority in England were actually Mark II (300+).
In terms of newly produced artillery, not counting guns evacuated from France (a total of 322 of all types or roughly one-in-eight had been brought back), there were about 140 2-pdr AT guns, 568 40mm Bofors AA guns, 294 25-pdr guns, 728 3.7-inch AA, and 118 other miscellaneous guns added to the Army from 1 April to 30 September. In terms of ‘B’ Echelon vehicles, 63,879 had been lost in France, but 54,057 new ones had been produced.
Also by that time the initial shipments of equipment sold by the US had arrived, including 895 M1917 and M1897 75mm guns, each with 1,200 rounds of ammunition, 300 3-inch mortars, each with 325 rounds of ammunition (enough for 150 battalions under current WE), 1,157 Lewis, 7,071 Vickers, 10,000 M1917 MG, and 25,000 BAR.
The best overall source for the recovery of the British Army and the development of the defense is David John Newbold, British Planning and Preparations to Resist Invasion on Land, September 1939-September 1940, PhD (War Studies), King's College, University of London. It is masterful; I am surprised it has never appeared in print.