When the line popped I topped up with 3 litres, the trans came back to life, well it got me home driving gently. The fluid was around 20 miles old no more than that. Topped back up yesterday and tried the dipstick when it was warm and idling it was low, barely registering in fact, turned engine off waited five minutes for it to settle and it measuresd perfect for a hot engine.
So it's a bit confusing, really want to get this sorted so I can take the car out and see if the box is damaged after what happened.
thanks for everyone's input on this, much appreciated.