How much do GCSE's matter when applying to Uni

So I'm taking my GCSE's in a few months and I'd like a quick tip as to how much my GCSE's matter in regards to applying for a UCL (using this uni for hypothetical reasons). I'm looking at around 7A's and 3B's (Without being optimistic or pessimistic). I acknowledge that your A-Levels are what really count, but would like to know if achieving those grades would prevent me from getting in to UCL.

Do your best. Not because your IGCSE's will help, but because they won't be a massive thorn in your side. It keeps options open.

On the other side of the spectrum, I had 3 A's and 8 B's and I received an unconditional from UCL for History. However, the pain and suffering I went through on account of my IGCSE's was ridiculous and I wouldn't want anyone with high ambitions to go through that. Do your very best.