a little heat was needed to free the bearing from the ally housing.
In the end I bought a new motor for a cheap price. I could have revived the old one but it had some wear and clearly water/silt had got in and not drained out. The price for new was very good (£70).
When I looked carefully at the winch plate that hold the drum and the motor, I noticed two small slots in the ally that would allow water and carp into the motor casing. The gearbox end is fitted with gaskets to seal it up, so I used a fair bit of hylomar on both ends of the motor and sealed these channels up.
The motor might need a vent fitting to it, but there is plenty of scope to drill the motor's casing and fit a vent line.
Looking at the winch they're not that bad. I think because they're made for the Australian market they don't perceive deep water or something!