'Being a Psychiatrist' is a career specialism following qualifying as a doctor.
If you want to be a Psychologist - an entirely different job - you will need a degree in Psychology, a Masters degree and a PhD, and years of experience. Most graduates from Psychology end up working in different careers as there are few entry level jobs and its a very narrow career field. See - Clinical psychologist job profile | Prospects.ac.uk
Most medical schools ask for Chemistry so you might be limiting your options heavily if you don't do Chemistry. Have you looked at the medical admissions forums? They have such comprehensive information probably every question has been answered so maybe head over there and ask away
I am nearing the end of my GCSEs and have started to apply to different six forms. I am hoping to become a psychiatrist in the future and was wondering what subjects would be best. Currently I have chosen Physiology, Biology and Language and Linguistics I have to fill 1 more block and I was wondering if its absolutely necessary I take chemistry or physics. I am not very good at either of them only being predicted a 6 in both of them. In other subjects I have expected grades of 7s and 8s for example English lit, is it acceptable to have it as an A level if I want to go into the field of psychiatry? If this isn't a good idea then will maths be a viable option instead of another science . Thank you.
I am somewhat confused as to what qualifications you are planning to study. I'm not aware of an A-level Physiology (unless you misspelled psychology?) nor in "language and linguistics" (unless you mean A-level English Language?).
But in any event as you can see from the above, the vast majority of medical schools require at least two "core" sciences (i.e. biology/chemistry/maths/physics) - sometimes they specify one or both of these.
Assuming you do mean psychology and not physiology (and it's rather important you understand they are two very different areas...), there would only be 10 UK medical schools you could apply to. Which then you would need to factor your GCSEs in (as if they were weaker you'd need to rule out all the GCSE heavy medical schools) and then your UCAT result (which if you didn't do so well in might rule out quite a few others).
The way to successfully apply to medicine is to a) do the research and understand what medical schools actually require and look for and b) do everything in your ability to give yourself the widest range of options of medical schools to potentially choose among, to ensure you end up with at least 4 choices that you could make a competitive application to.