After operation Bluecoat, 30th july 1944, some tanks crews that lost their Churchill mk iv tanks were replaced with the mkvii variant....this is particularly so after the first day of 'Bluecoat' when 11 tanks from 'S'squadron were knocked out at Hill 226, just south of Les Loges in Normandy.
My source of info comes from my Father who was lucky enough to escape with no injuries.
He was in 'Skye' tank, 8 troop,'S' squadron...and I believe the majority of the tanks replaced that day were upgraded to mk vii's.
Eain.