ive just had the same problem with a glow worm 24ci,take the front panel off,drop down the timer control board,turn off the little blue water supply tap,look at the filling valve and disconnect it by taking out 2 clips,with the tap in your hand look down the middle and you will see a white dot,poke it with a screw driver,its this that gets jammed when you turn it,after replacing do not overtighten,it did it for me,then turn the little blue tap back on.
daved,gateshead, January 2008