Brit Challenger 2

Challenger 1 , basic production mdoel

Challenger 1 mk2, Armour kits tested, Chobham side, Reactive front lower, long range fuel tanks(rear)

Challenger 1 mk3 (op.Granby, 1991), Added new radios, all round chobham armour on the lower hull, ive heard that troop leader vehicles had GPS fitted.

Challenger 2, new turret, gun, powerplant, tracks, basically the C1 hull shell with a refit.

Challenger 2 mk2 (Op Telic 2003) using the armour packs from the C1, extra skirting on lower side armour (urban anti mine and FOD), replaced the gunners GPMG AA mount with a normal pintle mount

Challenger 2E, export model fitted with lower grade gunnery system, ,50 cal mountings, no armour add ons.

Ah, perhaps I misunderstood.
Thought you thought Tamiya's kit was a Challenger II!

If you are doing a C I, Tamiya makes 2 versions, one having the thicker side armor. Not sure about the gun differences.

There are some good shots on www.reuters.com. In the upper right corner change from news to photos, and search for "british tanks".

Well, the Tamiya kit is a Challenger I, which, though quite similar to the Challenger II, is a different vehicle.
The only kit available is Trumpeter's C II, which I have and can recommend.