I think you've got your chronology a bit mixed up there - three ITV stations did launch in 1959 (Tyne Tees, Anglia and Ulster) but the very first was the original London weekday station Associated-Rediffusion in 1955, and that's the one that had Gibbs SR as the first commercial.
Thanks for your reply. Yes, I got the date wrong. Gibbs was the first commercial shown on commercial tv. But what were the second and third ads. shown? I know that lots were drawn from a total of 24 to have the honour of being the first. But what were the next two ads to be shown? The record books only seem to name Gibbs, the first.