Education and early career
He was educated at Canon Slade Grammar School on a scholarship but never completed his education there because at the age of 14 his talent as a singer was recognised by Herman Darewski who signed him up to tour with his dance band. When his voice broke he learnt to play the guitar and played in local dance bands whilst working as hat salesman then for Bolton Parks Department and later as a golf pro. He then joined Oscar Rabin's orchestra where he both played with the band and did musical arrangements, they also broadcast on the radio. He also worked with Geraldo but turned down an offer from Val Parnell to conduct the London Palladium Orchestra and chose in 1951 to join the BBC Northern Dance Orchestra, the BBC's then in-house big band, as its arranger-conductor.
Ainsworth achieved a huge degree of success with the BBC NDO whose reputation as one of the top bands in the UK was in no small amount due to his hard work and high standards. In 1956 he announced during Sunday Night at the London Palladium his engagement to Teddie Beverley of the Beverley Sisters. They could not marry immediately and in 1957 he announced that the engagement was cancelled.
In 1965 he conducted the orchestra at the Royal Command Performance at the London Palladium for the third time. He conducted in the Eurovision Song Contest five times, 1975, 1976, 1977 for Belgium, 1978 and 1990. He was the musical director for the BBC's anniversary programme Fifty Years Of Music broadcast in 1972. In 1978 He provided the music for the LWT show Lena and Bonnie and in 1979 Alyn Ainsworth and His Orchestra provided the music for the BBC show Lena Zavaroni and Music along with Alan Roper He provied the Musical Arrangements for the show.