Do I need FM to get into computer science?

For Imperial and Oxbridge most likely. Possibly UCL as well. Not sure about Durham. I think @Blue_Cow has indicated before Edinburgh doesn't especially disadvantage those without it so presumably not an issue there.

Think you'll probably be fine as long as you avoid Oxbridge/Imperial mainly. If you did want to apply to Oxbridge or Imperial then you'd probably realistically need to be doing it in a gap year unless your referee can attest that FM is not available at your school in their academic reference.

Note that the Russell Group tag has no influence on whether a uni is "good" either in general or for CS. It's ostensibly a postgraduate research consortium (therefore completely unrelated to undergraduate teaching) and in reality a political lobbying group. Choosing unis because they are or are not in the RG is not very smart, as you will miss a lot of very good unis that aren't members (and may end up applying to much weaker unis for your subject area that are in the RG).

Also the computing sector in particular seems quite agnostic to graduate's alma maters when it comes to recruitment and the emphasis seems to be on passing leetcode, having relevant work experience, having demonstrable coding projects on github, and doing well in the assessment centre activities (e.g. psychometric tests etc). All of those things are pretty much separate to which uni you go to (arguably quite a few non-RG CS courses may prepare you better for some of that due to having more emphasis on programming rather than computer science as a fully fledged academic discipline).

Equally though if your main impetus for pursuing a CS degree is to learn how to program and get a job programming, you would be much better off just doing a degree apprenticeship in a related area. As a CS degree is much more than just programming (which in fact can be a relatively small part of it).

What more important university ranking in the uk or international. Because there are some CS uni that rank very well in the uk but international they rank bad like 150.

University league tables are only useful either in very general senses (e.g. X uni ranks bottom 10 routinely in the UK vs Y uni which ranks in the top 10 in the UK) or for very specific criteria (e.g. spend per student).

International rankings are basically of no use unless you are actively considering universities outside of the UK - in which case chances are you'll find somewhere as good or better outside of the UK unless it's Oxbridge/Imperial. Comparing UK to international universities otherwise is a purely academic exercise that isn't of much use to anyone. If you're a home fees UK student who can't afford to study outside of the UK it's a moot point. Not even worth looking.

If you are an international student though then I'd wager you can find somewhere as good or better in Europe for a lot less, outside of Oxbridge and (maybe) Imperial.

For Imperial and Oxbridge most likely. Possibly UCL as well. Not sure about Durham. I think @Blue_Cow has indicated before Edinburgh doesn't especially disadvantage those without it so presumably not an issue there.

Think you'll probably be fine as long as you avoid Oxbridge/Imperial mainly. If you did want to apply to Oxbridge or Imperial then you'd probably realistically need to be doing it in a gap year unless your referee can attest that FM is not available at your school in their academic reference.

Note that the Russell Group tag has no influence on whether a uni is "good" either in general or for CS. It's ostensibly a postgraduate research consortium (therefore completely unrelated to undergraduate teaching) and in reality a political lobbying group. Choosing unis because they are or are not in the RG is not very smart, as you will miss a lot of very good unis that aren't members (and may end up applying to much weaker unis for your subject area that are in the RG).

Also the computing sector in particular seems quite agnostic to graduate's alma maters when it comes to recruitment and the emphasis seems to be on passing leetcode, having relevant work experience, having demonstrable coding projects on github, and doing well in the assessment centre activities (e.g. psychometric tests etc). All of those things are pretty much separate to which uni you go to (arguably quite a few non-RG CS courses may prepare you better for some of that due to having more emphasis on programming rather than computer science as a fully fledged academic discipline).

Equally though if your main impetus for pursuing a CS degree is to learn how to program and get a job programming, you would be much better off just doing a degree apprenticeship in a related area. As a CS degree is much more than just programming (which in fact can be a relatively small part of it).

Thanks for the reply. Do u have any recommendations on good cs university to go to?

There's plenty of good unis for it but without further information clarifying your position it's impossible to advise. I would recommend making your own new thread with further details about your grades, subjects, and where you are looking to study.

yo man quick question, im doing A level math currently and im not doing it in college im doing at home, also doing it in 1 year instead of 2. do you think that gives me any advantage when applying? like will universities see that do u think.

No, doing it earlier confers no advantage. Also if you aren't doing the equivalent of a "full course load" (i.e. 3 A-levels or equivalent) in one sitting (e.g. if you do the equivalent of 3 A-levels in one year and 2 in the next) then unis sometimes have issues with that.

You also run the risk of not fully grasping the material in the shorter amount of time and getting a worse grade and having to retake.

nah so rn im doing a btec level 3 in IT (equivelent to 3 a levels) and also the A level math, so equivelent of 4. im going onto do my final year of the BTEC and decided i want to do A level math, i got a 9 in gcse math and i rlly like math so i know i can do it in 1 year. plus im already half way through the first year lol.

Well it's definitely a gamble then. You won't get any "bonus points" for doing it in a year or anything. You'd be considered just the same as someone who did it over two years alongside the BTEC level 3 diploma.