Maths BSc - Durham/St Andrews or gap year imperial/warwick (if better grades)

Hi everyone, I need a bit of help.
I am applying for Maths BSc at Bristol, Durham, St Andrews, Durham, Warwick, and Imperial. My A-Level predicted grades are A*AAA in maths, physics, computer science, and further maths (AS tho), and I've just completed the TMUA Jan 2026 sitting. These grades corresponds to Bristol/St Andrews/Durham's requirements but Imperial/Warwick seems aspirational and unlikely (since I'm doing AS FM and not A-Level FM). And out of Bristol/St Andrews/Durham, I'm more eager to get into either Durham or St Andrews rather than Bristol.
My main query is if I should stick to Durham/St Andrews, or take a gap year and do full FM to reapply for Imperial/Warwick (or even Oxbridge) if I achieve much better grades. My ambition is to get a MSc afterwards at perhaps Imperial/Oxbridge, so is it worth taking the gap year for imperial/warwick to get a better chance at the MSc, or stick with Durham/St Andrews if the MSc doesn't see a major difference between the two undergrad pathways?
If i were to stick with Durham/St Andrews, then my second query is which out of Durham or St Andrews would be much better to choose from based on quality of student life and quality of maths degree.
I'd rlly appreciate an answer to this 🙏