Thanks for your reply.
Just tried again - still cant get any adjustment via the knob or fine adjustment knob.
It is as though there is no 'engagement' between the two adjusters and the shaft with the teeth cut into the back.
Also, the centre orange knob will not come out flush with the outside. It does click in nad out to some extent, but no where near flush.
There is no way of holding the depth of cut except using the locking lever.
The router has had very little use, so it would seem unlikely that the 'gear' connection would be damaged???