Found this description for bleeding the system. The valve would be on the plastic section of the top hose. The other (aluminium) pipe that you describe sounds like an air conditioning pipe. The bleed valve is on a pipe just to the lower right of the throttle body at the front of the engine. To open it, turn it a 1/4 turn clockwise. This allows air / water to run down a pipe at the back of it, back to the expansion tank. With the valve, open re-fill the system until water starts to come back to the tank via the pipe off the back of the bleed. Once that's done, start the car and run it with the heater on 29 degrees for 5 mins, topping up the tank as necessary. Once the water level is constant, close the valve and put the lid back on.