I would note something like 95% of successful applicants to Oxford PPE have A-level Maths. Additionally, generally Oxford emphasises GCSEs heavily in the admissions process in determining who they will shortlist and invite to interview, and on top of the PPE is one of their most popular courses, so there is a lot of well qualified competition already.
To be honest, unless you have significant extenuating circumstances for your GCSEs and the only reason you aren't taking A-level Maths is because your school doesn't offer it, I really doubt you would even get an interview. Perhaps if you take a gap year, take A-level Maths, and apply with very good (i.e. better than AAA) A-level grades already achieved, it might be a possibility. As it is, I think it's an unrealistic consideration.
As above, economics is necessarily mathematical at university level, and contrary to popular belief it is not just simple descriptive statistics as you'll have done in GCSE. You need calculus, perhaps a touch of analysis too, matrices (and perhaps some proper linear algebra), and all the associated "basic" algebra and functions work which supports that. If you aren't happy doing lots of maths, you won't enjoy economics at university.