I've been doing some research about aitch/haitch on the Web. The prevalent view is that 'haitch' is an Irish Roman Catholic thing, though no one can satisfactorily explain why they add 'h' to the dictionary word. For this reason, in both Australia and Northern Ireland, where Catholic educations are common, haitch is a bit of a shibboleth. People who have had Catholic teachers in this country are likely to say 'haitch', though a correspondent from Lancashire who had been taught by Catholics said he had always been taught 'aitch' (perhaps because Lancashire is home to a larger than normal proportion of 'Old' Catholics - i.e., English who never accepted the Reformation?). I myself went to an RC school for a while and had a number of Irish Fathers teach me, but they all said "aitch". I never heard "haitch" said until travelling in Ireland as an adult. I put it down to another amiable Irish eccentricity at the time. But it does seem from what I've read about it to be a bit of a tribal thing.