Best I can come up with would be 1976-1979. Geminair started up early in 1976 and the Brit was regular until 1981 when it was sold in Zaire. Last record I have of it was 5/3/81. G-APWY was repainted in a blue scheme by the time of this photo on 9/11/79. It was donated to the B.H.A.M Southend in Feb 1981, subsequently to the Science Museum aircraft collection at Wroughton. The 125 looks like McAlpine G-BBGU, which they operated 1973-1982.