In that case it sounds like you may need to recalibrate all your axis's.
There is a function that walks you through setting up your "steps per", so that your axis's move the correct distance they're told.
You'll find this function in the bottom left of the "Setting" screen, just above the reset button.
When it asks for a distance to travel start off small at first. Once you save those settings do the calibration again using almost your machines maximum amount of travel.
The longer the distance you use to calculate the steps per, the more accurate the calibration will be.

Ozymax, you hit the nail right on the head!! I did a recalibration of each axis and the work is now almost the right size (perhaps about 1mm out over 120mm). Strangely, I found some inconsistent results. Initially, the calibrations were out by a factor of approx 5 times. Having recalibrated the y axis, the error was down to about 2mm over 20mm. so I recalibrated and the error actually increased to around 15mm over the same distance. I recalibrated and reduced the error to 1mm. I left it so and did the other axis and ended up with similar small errors after several tries on each. Then I ran out of time.

Today I will spend some more time on each axis and over the full length of each axis to try and improve the accuracy.

Thanks again to you and Nick for your ideas and esp you for the solution :-)

Glad I could help.
Any inconsistent results would suggest either your measuring equipment or technique is flawed or you have backlash in your axis's.