hey guys thanks so much, i used the sealing ring on both parts, the nut against the wall and the black circle nut screw.
the filter was suprisingly clean and i just empited the water from this and retightned.
all seems to be fine and no leak
only issue i have is the water pressure still goes into the red on the boiler. i did refill to 1.5 but when i put on the heating for the RADS it does seem to reduce.
the main thing for now is
*no leak
*radiators are warming up
*i have hot water
there is nothing else i need to do with the filter area right, not sure what the screw section is onto of the filter. the screw head fits a flat head screwdriver to turn....
thanks again