To an extent, they all look at GCSEs, but some taken them into more consideration than others.
It's a case of doing the research of the universities you want to apply to and reading their requirements very carefully.
Also, I'm not 100% sure about what you have to declare on your UCAS. Someone might correct me here, or you may discover somewhere else, but you may not have to declare any grades that you think may bring down your overall application. I would think almost certainly though that you have to at least declare science, maths and English GCSEs to apply for medicine so it's important that you have good grades in these subjects