Another thing i thought of, ive used 5w-30 castrol GTX magnetec, you know that stuff you have for the modern Zetec i bought it buy mistake and only noticed when i was filling the engine

Ive done 0 miles with the oil in as ive barely started setting up the engine, im sorting out too many problems like this am planning to change it for the proper stuff soon as it'll probrably have swarf in it where i refitted the head etc

It only leaks when up to normal running temp, from cold its fine