The head tube and seat tube top lugs look like the windowed lugs on a mid-80s Raleigh frame I have; the catalog literature says that they're Prugnat for mine. I think your frame is somewhat older than that, based on the braze-ons. The brazed-on cable guides on the bottom bracket are “transitional” between earlier bikes of the 70s that had guides clamped to the down tube, and later bikes from the mid-80s that routed cables under the BB. I'd be tempted to say Raleigh, but with Campy dropouts a Raleigh would have a serial number beginning W, and the BB lugs don't have the characteristic scallop out of the edges of the lugs (straight cut in your case) that Raleighs do. If it's threaded English, then chances are that it's of English, Dutch, or Japanese [Tange fork: even in England, a Japanese frame might turn up] manufacture. In any case, it's clearly a good quality frame. Stronglight's right that the brake bridge and ends of stays at dropouts might offer clues.