Narkissos:
I double checked - the one I have is "The Septuagint with Apocrypha: Greek and English by Sir Lancelot C.L.Brenton and in it it says:
"From the 4th century and onward, we know of no definite attempt to revise the text of the Septuagint, or to correct the discrepancies of various copies. It is probable, however, that just as the text of the Greek New testament became in a great measure fixed into the same form, as we find it in the modern copies,something of the same kind must have been the case of the Septuagint. As to the Greek New Testament, this seems to have occurred about the eleventh century, when the mass of copies were written within the limits of the patriarchate of Constantinople."
So I guess its out there, now to find it