Hello, welcome to the student room, it's so helpful for questions like these so I hope I can help you.
I've finished my A-levels now and I did English Literature, English Language, Psychology and Film Studies (dropped Film Studies in the second year). You don't have to have taken Law at A-level to be able to get on a Law degree at uni, or so I believe so I wouldn't get too caught up in doing subjects that will help you to get onto a uni course. I've changed my mind about my degree course 3 times over the two years I was at college.
If you want to take Psychology, if I were you, I would swap it for Economics, I haven't studied it but I'd say Maths is more valuable, and this way would would have more of a range of subjects. I would say Psychology is definitely worth doing, it's so interesting and you'll learn so much. There's a lot of research and research methods to remember, it's a game of memory for the most part, but it's so fascinating, or so I thought. Psychology is also highly regarded by universities and employers. I enjoyed it so much that I'm going to university to study it.
I would say try to pick a range and choose the ones you think you'll enjoy. I know it's hard to know what you would enjoy but I'm sure you have some idea, subjects you've never studied before are good to choose (I hadn't done Film studies or Psychology before).
Hope this helps and good luck.