The wipers are back up and running again. All credit has to goto member chickfromcaithness. She had the same problem last year and gave me the solution after I PM'd her.
One of the electrical connections in the wiper motor carrying the voltage had snapped. There is a plastic cover which unclips from the motor (where the multiplug connector is). This has metal tracks inside it which carry voltage. I was informed by chickfromcaithness that when her wiper motor was removed and opened up that one of the metal tracks had a break in it. Once it was soldered back together it was fine.
I can confirm that my Megane also had the same problem. I have repaired the wiper motor connections and it is all ok now.
Just thought this might save someone a new wiper motor.
To add to this, on the subject of removing the wiper motor this might help:
You don't have to remove the wiper arm to remove the plastic trim (below windscreen); as the archive post states you only need to remove the trim section below the driver side - two screws and then use a flathead screwdriver to ease this from the rest of trim (about where trim is over the wiper motor). It now looks that you would need to remove the wiper arm to remove this trim section completely but no - again use a flat blade to ease the trim from it's plastic tabs.
You may need to remove the battery protection cover so the the motor can be removed with ease. Then remove the motor as says in archive post above.
Don't think I had a broken metal track when I looked at mine. I had previously sprayed with WD40 (no joy) and so just cleaned and dried the fittings inside and out including just bending the metal track ends up slightly so would make a better connection.
The plastic housing which holds the metal tracks is removed by releasing the four plastic clips around the sides of the motor.
Anyway, wipers worked after refitting & reconnecting the motor. Sweet joy !!! Thanks again - all your posts gave me enough info & the confidence to attempt this job myself.
P.S. It goes without saying that you should check the fuse has not blown (for my Y reg megane expression, it's the yellow 20 AMP one, bottom row, third from the right - fuse box cover located above where the bonnet release handle is) - these small fuses can be a bit of a sod to remove (two flathead screwdrivers may come in handy).