i did did gcse biology early and now have chosen it at alevel but feel I don't remember the content will this be a problem and if so what do I need to re learn
It should be fine I did A level biology and I basically forgot the whole syllabus over the Summer, but it all comes rushing back when you start. If you are really worried I would just brush up on the heart and circulation.
The AQA specification begins with biological molecules, namely carbohydrates, lipids and proteins. It would be a good idea to go over your digestion work, including enzymes. That will get you set up for the first part of A Level biology. The rest of it, you can take it as it comes. To memorise content thoroughly, it's a good idea to cover topics multiples times. Once in class, then go over it a few times in your revision too.
You'll be okay, you re-learn a lot of things in biology, and will cover anything that you need to know anyway.
The things that I had most difficulty with was the heart, cells/plants (photosynthesis), and DNA. If you want, you could revisit those briefly but I wouldn't worry as you will go through it all again anyway.