It could be a gastro infection, but I can't know that of course. IBS does make our tummies so sensitive and the smallest little thing can set off a flare. I find. Even just not getting enough sleep, or over sleeping can do it for me. So if you might be fighting something off, maybe that's upset your tummy?
I'm in UK too and yes it's been cold the last week and bleak rainy and miserable. The other night it wasn't much above freezing. Same temps as parts of northern Norway.
I don't know if weather affects you like it does me, but I feel like a whole different person when it's gloomy rainy and cold. Even my dreams feel messed up. And I wasn't doing so badly but today my gut went really loose again with no dietary thing that I did wrong. It sounds mad, but I think the weather, change of seasons etc and more darkness affects my gut as well as my mood.
Get a couple of hot water bottles, duvets, blankets. Wear anything cozy that you can find. I am wearing thick cozy tights plus trackie bottoms underneath my 2 sizes too big combats plus 2 pairs of socks!! And I am super lucky to be able to light a log fire in my room. So try to keep as warm as you can.
All that stress on the body can start a flare up. When I get a bad flare up, eating or not eating makes no difference. I might get 2 hours of sleep early morning then wake up and have to make a bathroom dash. Meanwhile tummy is empty of food.
It makes no difference if I eat 'safe food' or not. My gut will still be really loose and complain.
I hope you get times when it settles down a bit and you can 'coast' for a little while? I do get those times and am so grateful. But a flare up feels like it's never going to end. I know.
I hate IBS.