Dr Challoner’s in Amersham, 1977. But we actually had a card reader and a teletype and acoustic coupler, so we could phone (IIRC) Imperial College, stick the handpiece in the box when we heard the tone, and then run our decks and get the error messages printed out straight away.
(some people also had numbers of dial-up connections for other computers, no idea how they were obtained, but IC was the official one. Bet sysops loved us.)