Thanks - don't think I can PM yet as not enough posts? Edited to add I can send PM's but don't get the option to PM you. Perhaps you need to be a member for a little longer?The expansion tank looks lower than the filler neck so I can't see how just topping that up would fill the remainder of the system hence why the technical service bulletin advises filling via the neck.
Gerogemac - I have checked other posts and can email you some instructions I've gleaned if you PM me with an email address
Another common but sometimes very hard to spot leak point is at the bottom corners of the radiator, often just weeps slightly. Also the heater matrix can leak unseen into the passenger footwell carpet but you would normally smell antifreeze inside the car if this was the case.the car has been fine since filled and bled but still losing water slowly. Garage thinks it is from a hose and needs new seal - part ordered.