all advice much appreciated, filled it up with dot4 and that second set of eyes and discovered it was leaking from left front, don't know what "union connection" is but if it's the connection between copper pipe and body/through body to flexi pipe then that's what it is.
shame i'm not more mechanically minded otherwise i'd attempt dleeding the system and refilling myself, as i'm not it'll be heading it's way to the garage.
cheers again.