Unless you wish to apply to one or two colleges in Cambridge, physics will not help you at all.
I personally recommend you do your latter combo of bio, chem, french, spanish.... UCL and KCL in particular will LOVE this and if you enjoy it, you will find it a lot more worthwhile. At the end of the day you only need Bio and Chem - the other one/two subjects can be anything you wish (so long as they're no crit think/gen studies or along those lines)