just an update....we have used them succesfully!!!
no accidents in her bed at all...and first "accident" was on weekend during her nap at beachhouse....i think she had called out and noone came (we were at beach and I think mum fell asleep on sofa) and Ella will not get out of bed most of the time.....so cant blame her for it....and none since!!!
I love our brolly sheets - so easy to clean when there was an accident WOOT WOOT!!!!