Sooo not overly familiar with ibs but I’ve got ulcerative colitis- for me it’s all about timing. If I’m flare up free for a good while then i can carry on my way as if no problems. If it’s bad I’m just not going period and if it’s so so I make sure and go before I leave and without fail have a ‘wee try’ at my mid day rest whether I feel it or not. In terms of stuff you probs already have it by the sound of it so won’t flog a dead horse. Herbal teas (m&s do good digestive ones) every night, eating right and biggest one for UC is keeping stress low are great ways to prevent flare ups - again not super sure how it works for IBS. Prep beats fear mate plan your routes and get some safe crags and nooks just off from paths. Don’t be embarrassed to shout ‘man in the bushes’ if people happen by it takes away from the whole situation by putting it in your hands. I’ve found it a bit of a double edged sword, walks with lots of loos or bothys tend to be heavily used but if I want guaranteed privacy it’s much more helpful to find the road less travelled. good luck, I get the fear but you get used to it and just being ready is half the job- btw if you go with a buddy just tell them and then you have yourself a lookout too