If the BEF had more than about 30 Mathilda IIs fully worked up on the entire Western Front that might have made a big difference! According to Sebag Montefiore's Fight To the Last Man most of the Mathilda IIs that did get to France were half built and had to be hastily assembled on the battlefield. Main armament had to be zeroed in etc etc. Most were Mathilda Is, and even they made a substantial difference at Arras
In most of the 'tank battles' around the Dunkirk perimeter the BEF had to use Vickers Light Tanks and even Universal carriers as armoured units. Really makes you wonder what British tank procurement was doing during the Phoney War.
Valentine is essentially a more reliable, cheaper, easier to produce Mathilda II so not a substantial improvement, in France anyway (?)
Fight To the Last Man - great book BTW, gets across the almost apocalyptic desperation in France in 1940
I wasn't really comparing the Matilda's to the Valentines, nor was I saying that the Valentines would replace the Matilda's (although that is possibly an option).
The Valentine was first given to the Government as an option on 10th February 1938. It wasn't accepted until mid-1939, with an order being placed towards the end of 1939 for delivery by May 1940.
What if, instead, the government accepted it either in addition to, or instead of, the Matilda II, in Early/Mid 1938, with an order being placed soon afterwards. How many could be built and deployed by May 1940 ready for the Battle of France, and what effect could they have had?
Based on the fact that they are cheaper, easier to build and more reliable than the Matilda's, we could see double, if not more, the number of Valentines than Matilda II's available during the Battle of France, which would have had a major effect on the overall battle