First of all, well done on the amazing result!
To apply to a Russell group University, you need 5 GCSEs with grades 4 or 5 (according to Google). So I think you definitely qualify for an application to Oxbridge. Check the entry requirements on Oxbridge websites. That might give you some idea on what they are looking for.
Hope this helps.
PS. I am not an expert in this so, please feel free to correct me.