I had gastroscopy fairly recently. I didn't go for the near total sedation option, only the numbing throat spray. It was hardly pleasant, but it's just one of those things you just have to be strong about and get it over with. If I ever had to go again, I'd still go with the throat spray. The whole procedure only lasts a few minutes.
I was a bit uncomfortable at the back of my throat for a day or two after, and full of wind immediately after!
Coincidently, I also had severe anaemia (among other symptoms) and the reason for the gastroscopy was to test for Coeliac disease - anaemia seems to be a very common symptom. I had been blood tested for coeliac before the gastroscopy and my gut was biopsied when the endoscope was down there.
I don't know your symptoms etc. and I'm not a Dr., but have you been tested for Coeliac disease? It often goes undiagnosed, so it might be worth checking with the GI clinic/your GP before you go.
Coeliac disease is just a severe intolerance to gluten and is treated with a strict gluten free diet for life. It was the best thing to happen to me.