Yes. You do have a shot. Just look at individual unis and apply for ones that pot less emphasis on GCSEs and more on A-levels and UKCAT/BMAT. Alternatively if you think you'll struggle getting 4As, apply for something else and apply for graduate entry after you've completed your first degree. I got four rejections for med when i first applied and am now in the final year of a neuroscience degree. Applied to graduate medicine and have a couple of interviews. Im not saying its easy (GAMSAT is a killer) but if you're determined and med/dentistry is something you really want to do then you have to be willing to put in the hard work.
Also, lots of optom requirements are generally lower and as long as you have 5 good GCSEs (which you do) you should be fine. I think most places are ABB. I work as an an ambassador for my uni but we dont offer optom so not too sure if my facts are right. prospects.ac.uk is a good place to start..