Fitted a new clutch a few days ago... adjusted cable accordingly... however, there's quite a judder when I go from stationary, forward or backward.

Any ideas what might be causing this?

How much care did you take centralising the clutch plate?
Is the rear gearbox mounting in decent condition?

My 2cv has suffered clutch judder since I bought it, 110,000miles ago. With 180,000miles on the clock, I'm now looking to have a new clutch fitted.

By the way, is the clutch you've fitted, an original quality one? Valeo I believe. Others are rubbish, by all accounts.

My old clutch was fine... until it died. I had a new valeo fitted, but it will judder in first if the revs are low (my engine ticks over very low anyway) but its done about 90,000m so far and it seems fine.

Very common problem with Valeo since asbestos no longer are used to reduce heat from friction. The friction plate can’t cope with the heat and get glazed very quickly after the new clutch is installed. However other factors may contribute to the judder like clutch cable (always fit new cable) or clutch fork is worn or bend. Also the shaft holding the fork may have deep grooves in it casing the fork and shaft to vibrate, mainly in 1st or reverse gear. Worn out spigot bush (inside the rear of the crank shaft) another possible cause. Even sloppy input shaft bearing in the gear box can make the judder worth.
My advice is not to fit Valeo but it is too late and you may need to live with it or pull the engine out to investigate all the possible items.

Check the gearbox mount.

When the gear box mount is "kaput" it will left the gear box under braking not judder when driving off.

That's just not so. The gearbox mount contributes to clutch judder a lot.

I can add some to the advices already given. Judder can be caused of uneven pressure/friction to the clutch-dish. When the engine turn one revolution, and the frition between pressureplate/cluth/flywheel is not smooth, you can get judder. Typical is if you rev the engine, it disapears.

Can be many causes to this. On old clutches it can be oil spill or broken springs in the clutch.

It is always a good idea to rub down/mattening(problems finding the right words here ) the shiney surface of the flywheel before mounting a new clutch/pressureplate/release-bearing. Sandpaper is ok for this.
Then there is important not to screw one bolt at a time fully! But turn the bolt just a little bit and then move on to the next, and so on until they all are fully tightened. If you do not, it is possible to bend the pressureplate out of shape and it will apply uneven pressure resulting in judder.

as with all the advice about engine mounts etc did you take time to clear up the mating faces? any corrosion and or deposits of cluch dust can get under the face by the locating dowels and cause the pressure plate to be out of alignment. if its a spring one the tags that centralise the plate can drag the crap down.
wire brushing the flywheel to get rid of it helps ...usual stuff about asbestos yada yada yada...

Sean