It depends a lot on the uni. I assume based on your subject choice you are considering Cambridge - which has a particularly good financial support package for undergraduates, although generally most things are still aimed at lower-income students.
If your parents earn less than ~40k (i.e. you will receive some quantity of government grant as well as your loan) you would qualify for most of these bursaries/ grants/ scholarships. There's the Cambridge bursary, which basically doubles your maintenance grant (not the loan though) - up to a maximum of 3.5k. There's also quite a few scholarships for STEM students - for example I receive a BP scholarship of 5k a year (very competitive to get though - 10 scholarships available for any STEM student at Cambridge to apply for, also 8 other (generally Russel Group) universities have 10 scholarships available each). There is also the Sagentia STEM bursary worth 1k/year you can apply for (you have to apply well in advance of your first term though, I remember being really irritated at just missing the deadline because my college hadn't bothered forwarding the info on to me). If you play a lot of sport, you can apply for an award from the Hawks Trust - worth up to 750 pounds/ year, although it is rare to get the full amount, and many colleges also offer funding for top sports people - e.g. I get 75 pounds to support my sailing training, and if I receive a 'blue' (an award for being a top sports person in the uni) I can apply to have this increased to 200 pounds. Colleges vary a lot on their funding though - some are much more generous! There are similar funds for outstanding musicians - particularly if you sing or play the organ...
There are also scholarships for doing well in your exams (college dependant again though) - for example getting a first at my college (in any exam in any year) would earn you 400 pounds. Some colleges run competitions such as essay/ play writing/ music/ art competitions (which generally anyone can enter) so you could win a bit more cash through these.
Colleges also have 'hardship funds' if you find yourself suddenly lacking money - although they can sometimes be a bit reluctant to hand you the cash...