Aitch is correct but yes, in the UK, some people say 'haitch'. Sign of poor education.
If you ask them why, they will say it is because it has to start with H. Haitch for H.
So then ask them if they say fef for f, lel for l, mem for m, nen for n, rar for r, ses for s, xex for x, and goodness knows what for w!