Can I cut the lillies I have just bought in a pot?

If the foliage and flowers have died back, then yes, although, as you've just bought them, I'm confused as to why they'd need cutting down now. If the foliage is still green and perky, feed and keep watered so the compost doesn't dry out completely, and when the foliage dies back, pull it off, or cut it down. You can leave them in the pot and they shoiuld flower next year ,unless you think they need a bigger pot, or you can plant them in the garden.

Thank you! The reason I asked was I would have liked to put the flowers in a vase,indoors,(I bought them cheap)..but maybe I had better leave them till they die off :)

I think Misstiki wants to cut the flowers off her new plants and put them in a vase....? You could do this, but it rather depends on how tall they are and how long you want the stems on your cut flowers. If you remove any more than, say, a third of the stems of your plants, then you are removing an awful lot of the leaves, which are needed to be able to build the bulb back up for next year. My advice is - don't cut them and enjoy them as growing plants - they flowers will also last longer on the plants than in a vase.

We posted at the same time ;-)

Ha! Well done Sid!
I've decided to leave them alone,thanks for the advice!
Just joined today,its a great idea! :)