I'm not in UK, sorry for you. At least here we can insist on what meds we get. I'll refuse a procedure if they won't work with me.
I can't take generic propofol, and somethime it's the only kind places have. It's got sulfite, and I'm allergic. Versed is useless in my book and I refuse it in writing, hand it to them when I go in. I've had fentanyl, but that just makes me vomit for the next 6 hours and does nothing for pain either.
I'll take diazepam, related to midazolam (Versed), but not as amnestic and a better muscle relaxant. I take it an hour and a half before procedures because I have fibromyalgia and post-polio.
Beyond that there's not much available, so I am forced to do without. I've got a colonoscopy coming up in a couple of months. Hurts like all getout for 10 minutes, but no nausea, get to watch the show, can drive myself.