I wouldn't worry about it (:
Just chose subjects you like right now, your GCSE choices won't be too important. Make sure you have at least four good, solid subjects that you can take to A-Level. Otherwise pick whatever, if a university looks at your GCSEs it'll for the the grades only, not subject choices.
This is the Trinity College subject choice guide, it's a bit elitist, so unless you are planning to go to a top end university you don't have to pay too much attention to it, but Law is rather competitive so it may be useful to have a little look. A lot of unis don't admit it, but they like some subjects over others:
http://www.trin.cam.ac.uk/index.php?pageid=604
Try to get a good selection of the A1, A2 and B list subjects (for Law you'll want to lean towards the Arts subjects - but a few sciences are always useful) and try and keep the C list choices to a minimum. As I said, at GCSE level they don't really care what you picked, but too many C list subjects might restrict your A-Level choices, and the last thing you want is poor A-Level subjects, especially for Law.
English Lang, English Lit, History and Geography are all good choices. (: A language is always a good choice, and perhaps additional essay-based subjects would also be a good idea. I wouldn't abandon science completely, so I woud advise taking at least one ^^