Only have 3rd and 4th gear
 

Had a new clutch a month ago. Had the handbreak adjusted last
Wednesday. Could either of these events cause a gear selector problem.
It's a cdti, done 28000 miles and manual gearbox.Could the "selector bar fall off" like the recovery man said, or is it something more serious ?

What does the gearstick feel like? Is it all floppy?

The gear lever moves as if there are only 4 gears ie It moves from front to back and from side to side. It will select 3rd and will change to 4th. The travel of the lever seems to be left of the centre line , where you would expect to find 1st and 2nd.

Yes it is floppy the previous was my description of floppy

Is it as springy as before the problem or less so?

No, It's not springy

It does sound like a cable has either snapped or popped off the gearbox.

1 cable does forward back, the other side to side.

So the side to side cable has almost certainly popped off. They would have to be taken off to do the clutch and maybe didn't go back on quite right.

Fairly easy fix. Pop it back on, but access on some models means removing the battery tray.

Thanks Phil, Sounds like it isn't gearbox.
Could the handbreak adjustment have caused the problem?

No worries,
And no, the handbrake adjustment would not effect that at all.