I did edexcel for sciences and maths and now do ocr chemistry, aqa biology and aqa maths and haven’t seemed to have any problems so I don’t think that will be too disadvantageous. In honesty you do spend a while revisiting and building on prior knowledge and some things do change slightly however having nearly finished first year content I would say you don’t relearn everything and gcse provides a good foundation - I haven’t had to unlearn something I was told was true and learn the complete opposite for example