for general riding not specific DH – will 60a be good or do i need 42a?

60a is fine, and pretty grippy.
On the rear, I always use 60a on all my bikes, likewise 42a on the front, as they still last a good time and grip that little bit more.
Use 42a on the rear and it'll be worn very quickly, only really suitable as a DH only sort of tyre I've found.

if you can find them, 2.35 60a single ply DHFs (on both wheels)

Anyone got any comments as to how they perform generally in mud, wondering about using one on the front for more grip for general riding over the winter

very well.. but you need to be compitent riding in mud in the first place.