Born in 1958, Ewers studied piano and violin from a young age before settling on the oboe as his first study when in his teens. He played in school and youth orchestras and a range of jazz and rock bands before furthering his music studies at the University of Surrey (1976-79). At Surrey he developed an earlier interest in composing, studying with Robin Maconie and Reginald Smith-Brindle, and this became his main area of study. In 1979 he founded the Varèse Ensemble, a group specialising in the performance of contemporary classical music. They performed regularly at the Southbank and other venues until 1985 and gave the première's of many of Ewers' pieces from this period.

In 1980 Ewers continued his composition studies at Goldsmiths' College with Stanley Glasser, and was awarded an MMus in 1982. On graduating he was asked to take on some composition teaching and he continued working at Goldsmiths' until 1995. While doing so, he again furthered his composition studies on a part-time basis at the University of Nottingham, with Nick Sackman, and was awarded an AMusD in 1995.

Since 1995, Ewers has worked at Kingston University, initially as a research assistant and part-time lecturer, then as academic mentor to AHRC Fellow in Performing Arts, Jane Manning. In 2010, Ewers was appointed Director of Studies for Music, steering the Department through an Internal Subject Review and a complete re-writing of the three taught degree courses. In 2014 Ewers was awarded the Senior Fellowship of the Higher Education Academy and in 2015 became Associate Professor of Music. In 2018 he took early retirement with a view to spending more time on composing

Throughout this period, he has produced a wide range of music working with, amongst others, Quorum, The Varèse Ensemble, The Delta Saxophone Quartet, The Fibonacci Sequence, Gemini, Jane's Minstrels, The Wallace Collection and The Royal Liverpool Philharmonic 10/10 Ensemble. More recently he has worked with Torbjorn Hultmark on developing new music for the soprano trombone and with Kate Ryder for electronically extended piano.