Depends on where the Lancet hit but I've seen videos of a Lancet hitting T-80's and Panzerhaubitze 2000's and either doing very little damage or no damage at all. On a Challenger I can't see a Lancet getting through the armour (unless they significantly increase the warhead but that adds extra weight and the Lancet is pretty slow as it is) but it could likely damage the hunter killer system (if it hasn't already been striped out), optical sights, machine guns etc. So long as the hatch is such the crew should be safe.
I would be more interested to see how the C2 fairs against the Kornet missile but Kornet seems to be MIA in this conflict (in 2014 it was causing a lot problems).