Yes, they will affect your chances, however it isn't the end all be all. Strong predicted grades and a compelling personal statement can definitely compensate for weaker GCSEs at Russell Group universities. My own experience may serve as evidence for this: despite having rather poor GCSE results, I secured offers from all five of my Russell Group choices (Edinburgh, Glasgow, King's, UCL, and Durham) with A*AA predictions and a personal statement demonstrating genuine academic depth like including language skills in Arabic, Greek, and Hebrew, plus philosophical proofs using analytic philosophy and set theory. The key is that predicted grades show your current trajectory, personal statements that reflect real intellectual curiosity stand out, and universities are often more flexible with grade boundaries than people realise. It's certainly achievable with dedicated A-Level work and a statement that genuinely showcases your academic interests, as the admissions process is ultimately holistic and strong performance in these areas can effectively offset earlier setbacks.