People saying haitch can certainly be found all over the UK to some degree, but it is definitely far more prevalent in some areas than others, in the same way that words like owt or nowt or ain't are used commonly used in some areas but rarely in others. Or when a word gets pronounced differently in spite of its spelling, eg. arks in place of ask. I'd consider those to regional (or sometimes cultural) affectations. I suppose dialect is the correct term but what is dialect, if not a form of cultural or regional affectation?
A linguist can say whatever they like about something being standard or non-standard. Linguistics is a very broad discipline that concerns itself with more than just the formally agreed British spelling of a word. As far as I am concerned, if a word appears in all the approved British English dictionaries spelt in a particular way, then that is its correct form. The OED has an entry for haitch which says it's a 'variation' of aitch but if you want to know the etymology of the word haitch then you won't find one. It's a blank page. You need to go to the original source aitch to find out more.
Would you be in favour a system where people no longer had their spelling policed or corrected at all, even in education? What about in business? Should we just give everyone free rein to spell and punctuate as they wish, using the Linguistic's favourite argument that 'language evolves' and declare all 'variations' as equally valid and a matter of personal choice?
Should we allow definitely to become a word with two 'non-standard' spellings of definately and defiantly ? Ditto genuinely and generally? ^Because I see those mixed up, mispelt and mispoken on a weekly basis and have done since the invention of the smart phone. People now spell and speak as they have learnt to via predictive text, for crying out loud.
In the same vein, why should we continue to differentiate between then and than when it seems that half the population under 30 cannot?
If 'non-standard' is not to be considered incorrect, then why bother teaching a 'standard' for anything? How long do you think it would take for total language chaos to ensue and for the majority of children to be become functionally illiterate?