"Those ones" - This is just tautology This is a plural form of That one. Such as if you are asked a question of "Which ones are done?" It would be grammatically correct to say "those ones." Even if you don't like the phrase.
Davrel said:
"You am" - instead of "You are": this is something that (British) Northerners tend to do. "Am" is the first person singular conjugation of the verb to be. You are right to correct these people.
Davrel said:
The letter "H" when pronounced as 'haitch' rather than 'aitch'
Pronunciation is the thing you should be least bothered about. Accents are different everywhere you go.
I admit I do not know the etymological roots of "oftentimes" but I have never encountered a British person using the word (nor have I seen it in literature), so whilst it may
once have been a legitimate word in British English, it is not used today.
In British English, the addition of "ones" after "these" or "those"
is incorrect.
Pronunciation and accents, despite being similar, are not the same thing. You should still say "aitch" even if you have a Scottish/Australian/South-African/Chinese/etc. accent. If something is mispronounced (i.e. haitch) it is incorrect.