Jack,
From my travels out there, I have seen two privately owned and restored Matilda II tanks, with others in museums, a number of M3 Stuarts, Grants..... It would be difficult to know, as with distance and cost getting to events, a lot of these do not travel far from home, but more than you might think, I would say. Away from WWII, there a good number of Centurions. If you want to count cut down Matildas, Grants and Stuarts, that had been converted to bush clearance and dozing, there are a fair few, but probably only of use for parts, as too much is missing or cut away.
Over to Ray............ to see what he has found on his searches ..........