What is the highest salary you can see yourself earning realistically (UK)

why would u go study geography? not finance or economics seems like a pointless degree geo

Front Office is the only way to make over £200,000 in IB. I'm pretty sure VPs in the middle office aren't likely to make more than £170k.
Plus, I need the transferrable skills from FO to land a higher paying job at a Boutique Bank.

is there any other way to get a FO job if you never attended UCL,LSE,OXBRIDGE,WARWICK?

What year of study are you in? Which course?

year 12 economics

Do you know about spring weeks during first year at uni? This is when the IBs start looking for potential employees and invite successful applicants for work experience. Getting a spring week will make you much more likely to land a job in an IB as if you do well in the spring week, they can give you a summer placement, and if you do well there you may be offered a permanent job.

In the summer holidays before you begin university, it's best to start preparing a CV and cover letter for these spring weeks. Since not going to a target uni will put you at a disadvantage, you have to try and make up for it in other areas of your application. So start doing stuff now that will make your CV stand out e.g good work experience, volunteering, awards etc.

But be aware that some banks screen out non-target uni applicants and so may not even read your application. Though this isn't too common.
Target universities carry also carry great reputation which makes their students seem more desirable.

It's still possible to get into a top IB, but you need to show that you're better than the applicants from the 'target unis'.