Does anyone know if BP tablets and ones for high cholesterol affect donating?
Mine don't (over 50 donations,) but it might depend on the particular medication, and you fo have to tell thrm what you're on. I'm on meds for BP, cholesterol and type 2 diabetes, and to date (rules change every now and then,) they're only interested in changes since I last donated, or changes in dose. They will be interested in knowing about any medication you haven't told them about before.
If you can get on the site, you can check for common medications. If something isn't listed, you can phone them, which I have done in the past, and they were able to look it up and makes notes on my record.
They also have senior nurses at sessions who can sign off on any health queries (often the nurse doing your initial check can't do this) - it's happened with me a few times over the years, including my last session, as I'd had a minor gynae procedure a few weeks earlier.