He attended John Mason School in Abingdon, and then went on to study genetics at King's College, Cambridge.

After Bellowhead's dissolution in 2016, Spiers released two albums with Peter Knight: Well Met (2018)[5] and Both in a Tune (2021); the latter has been described as "an extraordinary collaboration between two musicians at the absolute top of their game".

[7] Spiers performs regularly in a duo with Jackie Oates, mostly but not just at Nettlebed Folk Club; Oates and Spiers released a joint album in 2020 called Needle Pin, Needle Pin.

[9] Several of Spiers' compositions have become English folk session classics, most notably the jig "Jiggery Pokerwork" (a homage to his first melodeon), and a tune encapsulating his views of the Conservative Party.

[10] The former piece is well known among melodeon players for its notoriously unplayable B-section, particularly the infamous "Bb of doom".