Hi Zoe,
I have just finished fixing a gainsburgh 10.5 SCL,
after trawling the web for information.
I removed the plastic pipe that the hose attaches to,
put the little ball back into the small tube/knob that sticks out towards the wall,
then using a small stick/cotton bud pushed the ball firmly into the hole.
To test the ball is secure, cover one end of the tube with your hand and blow into the other.
If the ball stays, its secure (be careful where you aim whilst you do it, in case you lose the ball.
I hope this helps.
Joe
July 2008