Lovely stuff!
Yes, as has been said, the decals are frequently too large to go where they should, but no worries. I've seen people use 10mm or 6mm decals for the Welsh Guards side-bins. If it helps, the Welsh Guards would also paint a letter or number within the squadron sign to indicate the Troop within a squadron or a tank within a Sqn HQ, like this:
Sqn HQ: A, B, C, D (D deleted following the change to four-tank troops after Normandy).
1st Troop - All marked 1
2nd Troop - All marked 2
3rd Troop - All marked 3
4th Troop - All marked 4
5th Troop - All marked 5 (5th Troop deleted after Normandy)
There was no differentiating different tanks within the same troop.
There would also usually be an uncircled star on the turret-rear and a circled star on the engine deck.