Applying for Computer Science without further maths?

Yes you would be disadvantaged by applying without Further Maths, it's highly recommended and is even required by certain colleges.

So by making an open application I allow for whichever college that only require A level Maths to at least consider my application right?

You can make an open application or just check which colleges do and don't require it. I checked on the website for you and you can apply to all of them except for Magdalene and Sidney Sussex. I would recommend applying directly to a college that you like the look of rather than with an open application because you're going to be randomly assigned to one of the colleges with the fewest applicants anyway; you don't get considered by all of the colleges with an open application so there's no advantage to doing so.

Phew ok someone in the same boat as me. I have taken FM to AS level though in year 13 when i realised (too late) that FM is basically a need for CS. It did give me alot of anxiety however I'm applying hoping to score well in the CTMUA and hopefully my PS is strong enough. Still, it is a disadvantage cuz FM shows them you bascially have the mathematical aptitude they are looking for. what subjects have you taken ?

Guess it depends on CMTUA?

In you personal statement talk about how you realised the desirability of fm too late and mention how you have taken time to look at furthermaths content yourself and talk about topics/ideas that interested you

You need to show them you have really strong maths skill