I think Arras, with Valiants (even if they only have 2pdrs) and a Matilda I with a 2 pdr will be a major defeat for 7th Panzer. This wont affect the fall of France much, but it could cause a lot of delay in the final envelopment of the BEF and 1st French Army. A bad defeat wont just cause the spearhead to pause while they sort it all out, the German command was already seriously worried about advancing too fast with open flanks.
One could argue that such a delay would in fact slow things enough that the French carry on fighting, but even if not, I can see a strong defensive perimeter around some ports, Calais at least.
Whether they try holding it would likely depend on how fast the French collapse in the south; once that has happened, there is no point in holding a lodgement, but even so evacuation will be a lot easier and they can get at least some of the equipment out. So less chance of an invasion panic, with probably a lot more confidence of how the Army can stop any German armoured attack.