(TLDR - need confidence to start learning, help?)

From my profile's description, you'll notice that I'm a British Born Chinese, currently in Taipei, but don't speak Chinese. By some monumental feat of psychological deep-sea diving, I am, somehow, horrifically ashamed of this fact. It's foolishly stupid, and yet I am (both... ashamed and stupid because of said feeling), holding this nonsensical belief that because, to all outwards appearances, I am Chinese I should speak the language (and not be caught dead speaking English with a snobbishly RP accent), when in reality I'm just a 香蕉人 (banana person).

I realise it's foolish because there is no shortage of people around the world whose parents have emigrated from their homelands and settled elsewhere and had children who do not speak their 'mother tongue'. However, what makes this terrifically foolish in my case is... I SPEAK CANTONESE!! Having been here for a couple months and exchanged numerous messages with my mother (a Chinese language teacher... albeit in Cantonese phonology rather than Mandarin/other varieties). But I've been adversely affected by those who dub either myself (understandable, I'm British before anything else) or Cantonese (not so understandable, but something I utterly loathe arguing about) as insufficiently Chinese. I can't even bring myself to attempt communication in a 雞同鴨講 (chicken and duck talking to each other) sort of fashion. The level of folly is such that I can carry full conversations with my parents in Cantonese with minimal use of loanwords with a more natural Hong Kong accent where my sisters cannot, but it doesn't matter a whit because they have no compunction beyond the most whimsical of reasons for learning Chinese (yes, they're as British as I am). My only "justification", I guess you could put it like that if you were feeling charitable, is that my written vocabulary is appalling (a couple hundred characters...) while my spoken vocabulary isn't much better, in all honesty (a few hundred, maybe a thousand, tops, on a good day).

Typical interaction consists of me at the shops, a person asks me something (presumably thinking, huh, a Chinese person, so far so normal), then I open my mouth, whereupon incomprehensible sounds with a faint hint of tones issues forth (accompanied by the person's thought train becoming a none so subtly hidden OMG WTF?!), then I slink away after stammering something along the lines of 不好意思, 我聽不懂 (excuse me, but I don't understand what you're saying) and hope to be promptly forgotten. Further, I've come across a number of, to put it as inoffensively as possible, "foreign Chinese" who seem to be at ease with the fact that they don't speak much Chinese, if at all, and wonder to myself, why?! ignoring the fact that... well, d'uh, maybe they're not ethnically Chinese at all?! Of those that are, a few will say the occasional phrase, typically 謝謝 (thank you), and I'll shout to myself (internally, of course) "aren't you embarrassed?!", making it worse, my mind will vocalise it in Japanese, because shouting it sounds better in Japanese for some reason or other (don't ask, I don't know), and again ignoring the fact that... well, d'uh, maybe they're not ethnically Chinese at all?!

Now, even hyperbole notwithstanding, this is tremendously insulting, I realise, both to the people involved therein (in cases past, present and future) and everyone in the world who wishes to learn a new language.

For myself, in the same situation, I agonise over the fact that I should say neither 唔該 (thank you for doing that for me), because this is an almost meaningless expression to Mandarin speakers, nor 多謝 (thank you for giving me th[is/ese] thing[s]), because it's usually excessive and unnecessary and yet still a valid response that maybe will clue the person I'm speaking to into the fact that I'm not a Mandarin speaking Chinese individual or perhaps not because I'll have made the effort to shake my Resting Bitch Face Syndrome, and so I consequently just use English or mutter 謝謝 with what I assume is the wrong tone set and/or ridiculously quietly, feeling grateful that whoever it is that I intended to say it to has left or just plain can't hear me.

(conclusion in comment)