Hi I have a knocking noise on my 64 plate very low mileage Twin Air, its been to the local garage who have checked the front suspension components and they cant find the fault. Has anybody had this problem and know how to fix it please.

Welcome, knocks are common my first guess is drop links, one of mine just failed but looked and felt when manhandling it, fine, these are cheap to replace if you can do it part price is about £15.

Is there a particular point it makes the noise, potholes, speed bumps, pulling away, or there all the time even on fairly good roads?

Did they check the front suspension arms? The bushes were worn on mine and after replacing these ( big job front bumper needs to come off) the car had a nice silent ride again on my 12 plate TA