Summer internship or grad scheme

I’m about to be a final year maths student at a target school in the UK (Oxbridge). Didn’t manage to get a summer internship this summer due to starting to become interested way too late to have time to have a proper shot at recruiting season. Have done a couple weeks work experience at a few very small asset management firms. 

Question is, is it worth applying to IBD grad schemes or should I be aiming for more internship experience, ie. applying to summer analyst roles? My course has the option to do a 4th year if I get a first in 3rd year, so I could still theoretically be a penultimate year student, but I’ve only been getting 2.1s (~63%) in my first 2 years so probably wouldn’t be doing this.

Don’t know if that would even be possibly but just want to hear people’s thoughts