Reapplying

So this I applied for mechanical engineering to: Oxford Imperial Durham Manchester and Leeds, offers from last 3 rejected from first 2. I am strongly considering reapplying next year and withdrawing my offers. But the thing is instead of Oxford I want to apply to Cambridge. I'm doing 3 as resits and that will increase my AS UMS scores to at least 90%. I am confident that i will get 4 a*s and if I am going to reapply i will do an industrial placement or work experience for a year.
How successful are such people ( gap year applicants who reapply to cambridge). What do you think my chances are. Anyone know of any similar stories or any gap year applicant success stories.
Any opinions are greatly appreciated.

PS my a levels Physics Maths Further Maths Chemistry.