UCAS application and GCSE as a private candidate

Hello,

I am currently studying a BTEC Level 3 Extended Diploma in Engineering at a College in London. I am predicted DDD (triple Distinction). I am applying to Brunel, Newcastle, Bristol, Leeds, and Birmingham for "BEng (Hons) Electrical and Electronic Engineering".

I will be 21 when I start University. From September 2015 - June 2016, I did GCSE Maths as a Private candidate alongside my AS-Levels in Economics, Business and Law. I managed to improve my GCSE Maths grade from a "C" to a "B". However, the application form is not letting me put that in as it says that I cannot be "enrolled at two schools at the same time". I did my GCSE Maths at a place called "East London Skills for Life". For the Universities I have applied for, it is quite important I mention that I have a "B" in GCSE Maths, as that is part of the entry requirements.

Also, in 2017, I did an IGCSE in Physics as a private candidate. I got a "C". Again, I am having the same problem: I cannot put it in. I did from the same institution as my GCSE Maths "re-sit".

How do I sort out these issues relating to putting qualifications on UCAS?