Just had a quick peer under my MK2 1.8 and, for the life of me, I can't see the oil drain plug. Is it tucked away somewhere hidden? In particular, what type is it (hex socket, square socket or normal nut) and its size? (2/00)

If it is the same as the MK1 then it is between the frount wheels, on the drivers side (RHD) and sticking out of the sump sideways (so you can't see it from the passenger side). The sump is between two pastic covers. But you don't have to remove any covers to get at it. When the car is on axle stands it is easy to get to. (2/00)