A good set of army-surplus thermal long-johns, thick socks, regular trousers/jeans, T-shirt, Fleece, then flying suit over that.... Ballyclava helmet, flying helmet and a pair of gloves.... I use a helmet with visor, which is even better... the only part of me that feels anyway cold are my hands, so I generally sit on them when I fly, and weight shift to steer.
Many layers are the key to this... and keep your top layer wind proof.
GD