I've only had my Mini aquaplaning once and that was when I took on a couple of Cooper Ss on a very wet Bruce Highway just north of Brisbane. They told me theirs didn't, so I guess my skinnier tyres weren't up to it. I can't imagine the 1800 doing it because of extra weight over the front wheels. When I was working in the UK in the early '70s I had to deliver a brand new Mazda 626 Capella (rwd) and bring back the customer's used year old Austin Maxi ( a sort of hatched 1800 - sort of....). It was about 100 miles of motorway and it was blowing a gale with snow just starting. The Mazda was simply terrifying as it skittered all over the place and I was dreading the trip back. I needn't have worried; the Maxi came back in an even stronger storm - it drove arrow straight at twice the speed.