As far as I'm aware, this is essentially a US vs. UK difference. Other examples where UK English has a /aɪ/ vowel and US English has a schwa include "missile", "volatile", "hostile", etc. which in the US effectively tend to be pronounced as through written "mis(t)le", "volatle", "hostle", etc.
First, British English speakers do not all pronounce things the same way. There is a lot of dialectical diversity in Britain. As you saw in the comments, nickson104 is a Welshman and he pronounces "want" a different way from what I describe in my answer. No one pronunciation is absolutely "correct," since you'd need to specify in what context you mean it. However, I guess you mean to ask about the usual pronunciations for foreign learners in particular. That makes things easier, since resources for teaching British English as a second language tend to converge on a standardized or generic variety. Throughout this answer, I'll refer to "standard" AmE and BrE, by which I basically mean the forms that dictionary pronunciation guides and the like tend to record (and that foreign students tend to learn in classes).
How "want" is pronounced (according to a British dictionary)
The Oxford Learner's dictionaries list the British pronunciation of "want" as /wɒnt/.
Context on what these symbols mean
The word "can't" is not pronounced with /ɒ/ in any dialect of English, as far as I know. It seems you mean [ɑ]: this is the vowel sound generally heard in "father," "car" (if you pronounce it without an "r" sound), and the American-accent pronunciation of "not."
In standard American English, the vowel in words like "lot, not, stop, robot" (we name the vowel in this class of words "LOT" for short) is pronounced the same as the first vowel of the word "father" (named FATHER); the symbol for the American pronunciation of both LOT and FATHER is [ɑ]. For this reason, many pronunciation guides based on American English don't use the symbol /ɒ/ at all, and always use /ɑ/ instead.
However, in standard British English, the vowel used in FATHER words (like "father") is different from the vowel used in LOT words (like "not, lot, stop").
The FATHER sound, /ɑː/, is pronounced pretty much as in the American pronunciation of the word "father." The vowel is "long," literally: it is generally held for a longer period of time than the LOT sound (that is what the symbol /ː/ means after a vowel).
The LOT sound, /ɒ/, is pronounced somewhat like a short version of the vowel in American "father," [ɑ], but more like a short version of the vowel sound in American "law," /ɔ/; if "law" has the same vowel as "father" for you, use a short version of the vowel sound in "fort" instead, but remove the "r" from the end of it.
(These are just approximate descriptions; the important thing is to be aware that there is a difference so that you can listen for it and learn more about it if you need to.)
The word "can't" has the long [ɑː] sound of "father"; it does not have the short [ɒ] sound of "lot". The word "want" has the short [ɒ] sound of "lot"; it does not have the long [ɑː] sound of "father".
General advice for studying pronunciation
Google doesn't pronounce words very naturally and sometimes has mistakes. A better way to learn pronunciation is to study English phonology so that you know what sounds and distinctions to listen for (especially the distinctions that aren't in your native language), then listen to native speakers in Youtube videos and things like that, and if you want to know how to pronounce a specific word, look up how it is transcribed in a dictionary that gives pronunciation and listen to it on a site like Forvo.
Best Answer
For heinous say: /ˈheɪ.nəs/ like greyness
— ɴᴏᴛ /ˈhaɪ.nəs/ like dryness
— ɴᴏʀ /ˈhiː.ni.əs/ like Phineas
The Canadian speaker in the first clip is using the phoneme we refer to as the PRICE vowel. This phoneme is by convention normatively written as the diphthong /aɪ/ in both Received Pronunciation and General American, but the exact phonetics for that phoneme vary by dialect and speaker. He appears to saying [ɐi] there. This is a non-standard pronunciation of heinous according to the OED. He should not be using the PRICE vowel there.
In contrast, both the American and the Australian in the second clip are each using the phoneme which we call the FACE vowel. This phoneme is by convention normatively written as the diphthong /eɪ/ in both Received Pronunciation and General American, but as with all phonemes, the exact phonetics for that phoneme vary by dialect and speaker. The American appears to saying [eɪ] there, and the Australian perhaps [ɛɪ]. Those are two allophones of the same phoneme, so exactly which gets used phonetically will not change which word one hears said. This is a perfectly standard pronunciation of heinous according to the OED because it uses the FACE vowel.
In other words, heinous should rhyme with greyness and anus, ɴᴏᴛ with dryness and sinus.
Quoth the OED
The OED gives a primary pronunciation for heinous in both the UK and the US alike with the first syllable pronounced like hay as in hayfields, the so-called FACE vowel. However, it also gives an alternate, secondary UK pronunciation whose first syllable is like hee as in tee hee, which is the FLEECE vowel. The OED presents no evidence that heinous is ever pronounced with a first syllable like high as in high school, which is the PRICE vowel.
Historical spellings dating from Middle English include both heynous and hainous. Its etymon, however, is French haineux, in Old French haïnos, haïneus, from haine hatred, from ha-ïr meaning to hate. So the “high” pronunciation was historically there in Old French and perhaps in Middle English, but never that I can see in modern versions of either language.
Other References
I have heard native speakers of English from the Appalachia region of the United States use the "highness" pronunciation, and like the OP found this peculiar. I have yet to uncover any documentation in support of this variation.
However, others have noticed this and called it wrong. For example, there’s a blog post by V. J. Singal from 2011 that calls this the mispronounced word of the week:
And in the PBS column “Beastly Mispronunciations”, they cite The Big Book Of Beastly Mispronunciations: The Complete Opinionated Guide For The Careful Speaker by Charles Harrington Elster, who offers this opinion: