tbh mate im not a transit man but not all egr valves have water running tho them, and the one i was thinking of was diesel and yours in petrol. ill check and see if i can find out what egr valve you have fitted.
First i would check the dipstick and see if it looks like oil or maybe over the mark, umm just a thought you sure you starter has gone? coz with losing that amount of water it could be inside the pistons and not allow it to turn over (not trying to scar you ). I think the best thing to do is remove the spark plugs and turn it over, if water pissis out then head off, if not then least you would know. you not got rac or aa ??