It's usually found beside the cottage cheese or speciality cheeses. I've found it in Asda, Tesco and Sainsbury so if you can't see it why not just ask a member of staff.
I've scoured our Asda and asked numerous members of staff but it's a no every time. Even tried to do a pretend order on Asda home delivery and it came up with a blank. Sainsburys have it near the feta/mozzarella which I thought was strange - but that's where ours is.
i have always been able to get it in sainsburys, and now my local tesco has started to stock it.
*** if you can not find any i could get some sent down for you to pick up at omagh bus depot, i do not know where in tyrone u are so this many not suit but let me know if you want some.