Pack away. I would imagine many of us look like drug mules with our stateside Costco purchases on return visits! If a controlled substance is prescribed, have the prescription. Over the counter is fine.
It's smart to bring a few months worth of any repeat prescriptions you are on. You may also want to research that they are available in the UK and if not, go on and look at alternatives. It may take a bit of time to get set up with a GP and get a script for your current prescriptions.
Food as long as it's not meat, dairy, fruit, or veg, you are fine.