I am not familiar with UK machines, but here I believe the baby cycle is a gentle cycle with an extra rinse. You might google different manufacturers and look at the online owner's manuals.
The only machines I know of that have a dedicated baby cycle are Hotpoint Aquarius and Aquarius+ models and LG washing machines without steam as the baby cycle is replaced with allergy cycle on the dial on steam washing machines.
My aunt has a Hotpoint Aquarius+ WMF740K which has a baby cycle but its never been used. All I know is that it washes at 40oc with 800rpm spin with a 2kg washload and takes around 2 hours.
Someone who owns any of the above machines could explain more as to what the cycle does. I suppose it holds the water at a certain temperature to remove stains such as baby food etc.