It is quite possible that the Ant had a few 1100 bits - after all BMC were masters of raiding the parts bin - but the running gear is decidedly different. A-series engine, but a unique gearbox and transfer case. The engine is tilted on about 20 degrees angle. The tailshaft (being 4WD) passes inside the double-skin floor (would have been a mungrel to work on in the bush).
There appears to be plenty of room for bigger wheels, so perhaps the 12" were a stop-gap while the car was sorted.
The Ant was a fair way into pre-production, with so many cars being tested around the world, but was shelved, like the Austin Champ, when BMC took over Land Rover.
By the way, I saw an Austin Champ yesterday at Picnic at Hanging Rock, and I've always been impressed with them. Very capable, but much more complicated, mechanically, than the Land Rover, so not surprising they were canned.
Imagine if the Ant had gone into production, 20 years before the Suzuki LJ50. It probably would have failed when Leyland took over anyway, but the Japs are, or at least were, masters of producing good cars cheaply, and have no qualms about copying other people's design, so the LJ probably still would have been much the same success that it was.
Cheers,
Watto.
