Your both right!!!
According to wikipedia it was released as a double a side.
"Mull of Kintyre" was recorded in August 1977 in London, during a break in recording the London Town album caused by Linda McCartney's advanced pregnancy, which led to the departure of Jimmy McCulloch and Joe English from Wings. Bagpipes from Kintyre's local Campbeltown Pipe Band were included as a prominent part of the recording. The recording happened on August 9, 1977, with Paul's vocals and acoustic guitar taped outdoors. "Mull of Kintyre" and "Girls' School" (a rocker that had been previously recorded for London Town) were released as a double A-sided single on 11 November 1977, independently of the album. It was included on the Wings compilation Wings Greatest in 1978, and the UK/Canada version of McCartney's 1987 compilation album, All the Best!.
catch up...cats and kittens...don't get left behind...