I’m from wales so I sit the WJEC papers, but they’re pretty much the same everywhere:
I had an A* in GCSE and have just finished AS (early because of corona), I’m finding the course very interesting and engaging but much more difficult than GCSE.
At the end of the day if you done well in GCSE you’re very likely to do well in A-Level because the exams are in a similar format but you will have to revise and do work at home after every lesson if you want to achieve the best possible grade. (Which I didn’t do and had to catch up later on which was a pain)
The biggest issue for me was -apart from the huge workload between the religion (mine is Sikhism), ethics and philosophy- was timing. For most (might be all can’t remember) there’s 18 mins per question which is hardly any for the amount of information needed in each response; so timing is definitely something I would suggest you practice, maybe even before the course starts to get ahead of the game.
Overall, if your good with essays and learning a considerable amount of information and able to use it in a small amount of time for each question, go for it. It is definitely one of my favourite and interesting lessons but it really helps if you enjoy the subject.
Any questions about the course feel free to ask, however I can only give you definite info about the WJEC papers as there are slight differences.