*Update*
Been eating a rather bland diet for the last few days:
07:30 = Porridge with Milk
10:00 = Banana
13:00 = Chicken or Ham on 4 rounds of Wholemeal & mint club.
18:00 = ~150g roast chicken breast with 50g (dry weight) wholegrain basmati rice & 60g lemon swiss roll
21:30 + 6 melba thins with organic peanut butter only if been to the gym.
Can't really say that I feel any different though, going to swap out the rice for pasta next.
Being honest, your list does not strike me as a less varied diet, perhaps compared to what it was but if you have made changes and find no improvement, then I would personally opt to strip it right back.
I’m no dietitian but personally I would lose the ham (processed meat), club and swiss roll (massively processed and no nutritional benefit at all). You also have a huge amount of wholemeal in your diet so I would drop them as if you have a gluten intolerance then that would really set you back.
All this of course depends how much you really want to identify what causes the problems but having had this for a while I bit the bullet and did something like this:
Drink – still water only (avoid sugar-based drinks, tea and coffee)
Food – white rice and roast chicken
I did this for 2 weeks (yes it was utterly boring but IBS symptoms did go) and after a few days (personally I would give it at least 4 to 7 days or until you’ve had a few days free of IBS symptoms) if you don’t get relief then possibly swap the rice for something else such as lentils or even cauliflower rice (incredibly easy to make).
Thereafter you could introduce porridge (not the ready packet stuff) and with water. See how you go with that for a couple of days and then introduce one thing every other day. Writing down what you ate and what time you ate it could identify if IBS is linked to eating at a particular time of day.
After a few days (if all is well) then introduce a piece of fruit every other day. Perhaps a herbal or green tea (unsweetened) but whatever you introduce you need to give it a good day or two (per food) and personally I wouldn’t introduce more than one thing at a time otherwise you won’t know what triggered the IBS.
I suspected I had a gluten and dairy intolerance but actually for me it was eating fruit or drinking wine after 8pm gave me excess stomach acid and drinking any caffeine after 6pm along with foods like chorizo and most processed meats.
Edited to add: I was tempted to cheat by speeding up the process but at the end of the day, the thought of having to start again to identify triggers kept me going.