Possibly apprenticed to Timothy Lawless and/or William or Charles Hull (Gillen).

William Telford established his organ-building and pianoforte 'manufactory in 1830 (Gillen). In 1847 he took his brother Henry into partnership and some organs from this period bear the nameplate William and Henry Telford, but more normally Telford & Telford until 1870. Henry died in 1866, and in 1870 William's two sons, William Hodgson and Edward Henry, joined the firm as it became Telford & Sons (Gillen).

The Telford family firms were the leading Irish organ builders of the nineteenth and earlier twentieth centuries. As well as repairing and rebuilding many older instruments in Dublin and throughout the country, they build over one hundred organs in churches and cathedrals throughout Ireland, and many instruments for colleges, convents, private houses etc. Telford's reputation was such that in 1847 the leading French organ builder Aristide Cavaille-Coll invited him to inspect his new organ at the Madelaine in Paris, while in 1851 he was invited to be adjudicator at the Great Exhibition in London.

[Dates and addresses differ according to sources: the Dublin Directories give 108 Bride Street from 1832 to 1834, 45 Bride Street from 1834 to 1837 and 109 St Stephen's Green from 1837 to 1885. Boydell's (Card Index) gives 108 Bride Street from 1832 to ?1836, 45 Bride Street in 1834, 45 Telford Street in 1836 and 109 Stephen's Green W. in 1840, 1842 and 1843. Gillen gives 1830 (without an address) and 45 Bridge Street from 1834 until 1837, when he moved to 109 St Stephen's Green 'where the Telford firm was to remain throughout its existence'.]