Hello, I know exactly how you feel as I was unsure too. Luckily I have a friend who had an edoscopy under sedation and said that she wished she hadn't bothered, so that convinced me to just have the spray.
It was over in about 7 minutes and the spray wore off after about half an hour. The spray did make me panic a bit, because it felt like I had a ball stuffed at the back of my throat when I swallowed. SOme people say that they feel like they can't breathe, but I was ok there.
Gagging is a reflex, so there's nothing you can do about that, but the nurse I had was great and suggested I breathed through my mouth (a bit like you do in labour!) so I only gagged twice and that was it.
It's not a painful experience, just weird! I'm at SRH and they take a biopsy to check for H.Pylori bacterium (campilobacter), which it turned out I had. Antibiotics sorts that though, so again, it's nothing major...although I did have a freak out at the time haha!!
Hope this helps xx