I remember having this phenomenon demonstrated to me during slalom flying in the RAE Bedford Puma many years ago - full lateral cyclic to one side to hold a turn in the opposite direction. I further recollect that the Bo105 was mentioned at the time as having a similar characteristic, but reversed in terms of turn direction.
I think it's an Lv/Nv issue ie aerodynamic, and I think it's mentioned in Gareth Padfield's book.