Simon,
The Churchill tanks were used to equip the British independent Tank Brigades. The Tank Brigades could then be used to support any particular division. So you will not get a Churchill as part of the 50th Infantry Division, but would get a Churchill from an Independent Brigade fighting in support of the 50th's infantry. Which I presume you were looking for.
The following Independent Tank Brigades were in Normandy - but I'm unable to figure out off hand if any were assigned to support the 50th during the Normandy fighting.
4th, 6th Guards, 8th, 27th, 31st, 33rd and 34th.
The Armour in Focus site provided by AlanL above contains markings and some support assignments for the 31st, 33rd and 34th (see the 31 ATB, 33 ATB and 34 ATB) links on that site. I also know that the 6th Guards operated Chruchills and was mainly attached to the Guards Armoured Division (serving just to the East of Caen).
Also as far as I can gather the 50th Northumbrian Infantry Division did not really take part in any of the Caen fighting. It was part of XXX Corp which was over 10 miles to the west of Caen and seems to of taken a Gold Beach -> Bayeux -> Tilly-sur-Seulles -> Villers Bocage route. The Caen fighting was mainly the British I Corp and the Canadian II Corps which landed on Sword and Juno beaches closest to Caen.
Of course many of the roads they fought across would of eventually lead into Caen, it just depends how Caen specific you intend your diorama to be
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Hope this is of some help.
Chris
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