OK - I wasn't aware of the risk.
Put a pot of Lilies (pink ones) by the back door this morning for DH to plant in garden as they were dying (they were a gift). Cat had a chew of the leaves and they went out immediately afterwards.
Cat was sick within about an hour and brought up a couple of the leaves.
Cat seems absolutely fine. Drinking, eating, has been spark out for a couple of hours but that is absolutely normal.
Have been googling and have completely terrified myself.
Should I phone emergency vet now or leave it until tomorrow morning for further advice. He is 7 and fit and well.