Worcester Boiler (24 cdi) Bleeding/filling problem

[Preacher]

Hi Chaps,

I'm attempting to bleed/refill/repressurise my boiler, as the pressure has dropped to about half a bar. The problem is this:

The filling knob (small grey/black knob) keeps slipping and hence not turning the little whiteaxel/shaft that its attached too and so I can't (it seems) let any water into the boiler. I thought maybe that the knob was was broken or not gripping correctly as it appeared to have a touch of rust in (theres a small metal band inside the plastic knob) so I got a new one, but its made no difference. So my concern is that somehow the filling 'thing'(valve? sorry for the lack of the correct terminology) is broken/seized up?

Just to check (i know it sounds stupid) looking at the knob from directly below do I turn it clockwise or anti clockwise?

Cheers for any help

 

[COG]

The filling knobs do get tight and sometimes need a pair of pliers to get them going. look on the inside of the boiler case for instructions as to what way to turn, if your right handed then its your thumb going right to left as you turn it