Hi Fredrik,
I sympathize. Have you attempted the FODMAP (Monash univ. in Australia) diet? Its not in an of itself a cure - butt (aha) it does provide the first applicable helpful food info I've seen since acquiring UC at 10 year old. I'm 54 now with no colon having had UC then getting cancer. I tried every most diet, drugs, regimes..its the autoimmune disorder we stuck with having to treat symptoms to manage daily life. I struggle with this as well, I really don't know how to get through some days.
the itch is awful. some things to try:
the drug Questran is a bile acid reducer that can contain the itch if thats the cause of itch for you. its a script here in US.
sitz baths with epsom (make sure you dry completely after)
washlette /bidet toilet seat attachment
the creams are many -
calmoseptine otc, nystatin (via script here in states), dimethicone wipes when all else fails, anti fungal creams for bottom, line undies with some gauzy cotton fabric to contain the cream :-)
and my fav is sun..open it up to the sun. Feel better