GCSE’s affect which A levels your school will let you take (and how likely you are to do at them)
A levels affect which uni and which course
So, GCSEs are part of the gateway to the course you want to study at ether place you want to attend (I.e. they are an important stepping stone)
Outside of that, the English gcse result is important for uni and many set a minimum grade in English to attend other courses.
Unis will also consider your gcse results to some level when deciding whether to make you a offer (expected grades for a level are someone’s guess, existing gcse results are a factual representation of past academic importance)
I don’t say any of this to worry you, more as an answer to your question. If your results were not as good as you had hoped, uni and the course you want are still very much open to you…. You may just have to course adjust on your plan of how to get there (take resits for example, take a year out after a levels to apply with actual results, go to a uni that offers a foundation course etc)
Hope that helps