It doesn't really seem like you're massively convinced that you actually want to do biomed if you're considering chemistry. I was sure that I'd enjoy biomed because I read into the course, checked out the modules and thought that it was something that I would really enjoy studying. I've posted this elsewhere before, but it answers your question, so I'll paste it here:
You have your core modules, which are:
Proteins, Genes and Genetics - lots of biochemistry/molecular biology. Protein structure, DNA replication, transcription, translation, genetics, bacterial genetics.
Physiology and Metabolism - more biochemistry. Metabolic pathways, physiology mostly focuses on musculoskeletal and nervous system.
Agents of Infectious Disease - virology, immunology, microbiology and lots of other fun diseases
Cells, Tissues and Organisms - cell biology, a bit of embryology.
Quantitative Biology - biostatistics. Universally hated module, although it's necessary. It's being changed a lot for this year, as it was new for us and didn't receive great feedback.
Then your optionals (2 modules, 1 if you take Brain and Behaviour):
Brain and Behaviour - run by the psychology department. Lots of psychology/neurobiology. If you take this, it's your only optional module.
Health and the Community - similar to Agents of Infectious Disease, but more in depth on specific diseases and certain epidemics. My favourite module.
Animal and Plant Biology - mostly animal/plant/human evolution, with a bit of extra plant stuff thrown in. I took it, since I took H&C and I didn't enjoy it for the most part.
Environmental Biology - lots of climate type stuff. I don't know too much about it, as I didn't take it.
Then on top of those, you have tutorial work (two graded essays, one at 1500 words, one at 3000. A group poster presentation and an individual presentation) and lab work (biochemistry, microbiology, physiology and genetics labs). Labs are once a week for about six hours. You'll have to write a lab report for each lab, which are usually around 1,500 words or so.
I really enjoyed my first year. There's a LOT to take in, so my advice would be to study throughout the year to keep the material fresh in your mind. I left revision to a month before exams and it caused me a ton of unnecessary stress.