I went to the diamond light source a few weeks back in Oxford and I met a few scientists.This one scientist did a degree in chemistry but now she's doing more physicsy kind of stuff. The girl that was giving the talk did biology at university and she helps set up experiments related to finding out structure of proteins and stuff for pharmaceutical companies, but the experiments used high energy x rays, so it was like the perfect interface between biology and physics. One of the guys did chemical engineering and he told us to just do what we like at university and feel happier studying because your university course doesn't determine your future job in most cases.
Natural Science sounds more like you're kind of thing though, where you can do biology and physics whereas biochemistry isn't far into physics at all.