Call the uni and ask. Most have extra grants for those on low income, who have good grades, or with children or health issues. There will also be some sort of hardship fund available if needed, but that's more for emergencies.
If you aren't getting the full loans, that usually means your parents make over the threshold and the government expects them to chip in towards your costs. Many students also have part time jobs such as bar work, retail, and there are usually on campus jobs avaibale, such as note taking or supermarkets. If you can't work and study, maybe taking a gap year and working over that year to leave you money for your university years. Graduating at 21/22 won't affect your life, especially if during that time you've had money to eat. Also worth remembering that private renting is usually way cheaper than on campus dorms, so you will probably pay less in the later years.