While I haven’t applied to that course or to Bristol (went to UCLAN), I did do a 90 credit btec in applied medical science and achieved a D*D* (couldn’t complete the second year due to illness). I was instantly accepted at uclan the following April (applied late) to study a foundation year, with no work experience etc.
BTECs are a well received qualification now. You shouldn’t be at a disadvantage at all.
I think if you’re set to receive a full diploma with D*D*D AND work experience in related areas, I think you’ll stand a strong chance against many a level students (who probably haven’t had the chance or been able to do work experience). I would make sure your personal statement shows how passionate you are, mentions your work experience and how this sets you apart from a level students etc, and is really well written/concise. I don’t think you’ll have an issue, be confident in yourself!!! You’ve achieved a lot and are on course to achieve a top grade for a tough BTEC (it is no less difficult than a levels).
Hope this helps!
Good luck and best wishes,