Taking Extra Gcses

Hi,
I'm a year 12 student and currently doing my A levels as well as my Gcses. I'm only taking 4 gcses maths english turkish and science double award as an external candidate from a private exam centre(double award might count as 2 not really sure).I didnt know taking only 5 gcses might be a bit of a problem when applying to uni back at the time when I chose only 5 subjects. Uni entry requirements are usually 2 3 gcses but when you have a look at the statistics doesnt really seem that way people tend to have around 8 9 gcses. I was wondering is there anyway I would be able to add any gcses? I cant register now for more gcses as all the centres have stopped the registration for the exams since there's a month left. Hopefully I'll be starting college this september for year 13 and a friend of mine said maybe they could add predicted gcses just like how they do it for the A levels ? I really dont know how to get around this problem.. Any help is much appreciated thanks a lot.