is it hard to get into prestigious universities for med/dentistry?

Prestige is the last thing you should be considering for medicine, as where you study medicine will not directly affect your medical career in the UK - foundation training posts are pretty much randomly allocated now I gather, and specialty training posts blind recruiters from your medical school to ensure there is no bias.

You should be choosing medical schools on the basis of your overall profile, not whether they are "prestigious" or not. As one profile could be strong for one medical school and weak for another.

For dentistry since there are so few dental schools in the first place they're equivalently "prestigious" anyway. Cambridge doesn't offer dentistry anyway.

In either case you should be aiming at medical schools or dental schools that are not GCSE heavy (e.g. Imperial or UCL for medicine), avoiding ones that are GCSE heavy (e.g. Cardiff or Oxford for medicine) and aiming to do well in the UCAT.

thank you so much for the advice. and yeah i just meant like Russell schools. So would u advise me to apply to cambridge for med? since they aren't as gcse heavy, and since it was an existential crisis would all if not most med schools accept these grades?