In my GCSE’s I had an 8 As incl A^ in further maths but I didn’t get to interview. Admittedly I didn’t try very hard but still. I also know someone who is much better than me and didn’t get in. This is for maths at Oxford, I don’t know if physics is less competitive. But I know some really smart people who just missed out with much much better GCSE’s, incl. 9 As missing out for natural science at Cambridge. Essentially it’s pretty unlikely for you, but that’s probably for the best as these unis are really intense anyway. I know for me I definitely don’t work hard enough to be able to be able to go there. There’s no harm in applying but that’s just my personal experience