Which page on the website indicates engineering is an option...?
The only thing I could see would be at a stretch taking Bioengineering and Management modules - but the relevant BE ones you could take would essentially be covering the biology you already know, and the management ones aren't engineering. So...there would be little benefit. Your DoS should be able to advise you in second year, but I doubt it's possible.
Pursuing e.g. Biochemistry or Genetics and doing a systems biology oriented project, or PDN and doing something related to prosthetics or tissue engineering would probably approximate the engineering design and quantitative/physical approach while also developing your knowledge, rather than "retaking" content in a slightly different format. That would also be a reasonably basis to pursue many of the interdisciplinary areas between engineering and the bio(medical)sciences in a PhD/MD. You may even be allowed to do Part III Systems Biology after the Part II, although that would presumably be at the discretion of the college and departments, and you'd be more productive if you went into an MBPhD in that area rather than delaying your graduation (and clinical placements) by a year for not much benefit.