I think a lot of your queries can be solved with a deeper dive into dental admissions online. Anyways, to my knowledge, the most GCSE-heavy dental unis (aka ones you definitely shouldn't apply to) are Queen's University Belfast, King's, Cardiff, Leeds, Glasgow, and Liverpool (for Liverpool and Manchester and Glasgow specifically you'll get instantly rejected as you don't meet minimum requirements) (in this order). Otherwise, with the rest of your choices, I'd say a good aspiration (provided you get decent A levels and a decent UCAT) would be Bristol or Barts, and as more of a backup (although really there aren't any backups in dentistry) Plymouth. I'm not entire sure about Newcastle but I remember hearing from the open day that GCSEs are considered (but I'm not sure abt that and can't be bothered to dig through lots of notes) so if that's one of your choices I would do extra research on that.
*edit - just realized you have a 6 in maths so that kind of restricts a lot of your options, such as Bristol and Barts as I've listed above, so I'd do a bit more research on where you actually can apply to.. the only one I can think of is Plymouth