Phys natsci gap year?

I am thinking of taking a gap year to apply for phys natsci. I was rejected by Oxford this year, and would like to have another attempt at it (not at Oxford though, as I think I chose the wrong course). I would be aiming for Cambridge and Imperial, and was wondering whether taking a gap year would hinder my application. For context, I have a good set of grades, some work experience, silver in the chem and phys olympiads (not massively proud of those but oh well), an independent research project, and relevant further reading + extracurriculars. I would ideally undertake some kind of placement and possibly do a CREST project as well as some tutoring during my year off.
If anyone has done anything similar to this, your advice would be greatly appreciated! (Also some placement or longer work experience suggestions if you have any)

Sounds like you've got a lot planned. Universities will not discriminate against a gap year applicant but they will want to know what you have done with your time and how you have used it to continue studying the discipline.

Did you not apply to other options this year too?