Did you have them outside?
You should try and not leave fragile tender plants (most annual plants) exposed to the elements until mid May, if possible. Try and not get sucked in by occasional nice days as the nights are still far to cold for the plants!
Try bringing the Tomatoe plants in and see what happenes. If you are lucky they might recover! Good luck!!!

Ive got my tomatoes in my greenhouse, ive got a heater on a low heat.
Trouble is ive got so many from the 11 varieties im growing i dont know whether i wioll be able to sell them all.
But the tomatoes should not be planted outdoors until mid may, if you are growing them outside for the fruit

thanx for your replies, i had a heater on in the greenhouse but the heater went out when we had a very cold night. I have been told that getting water on the leaves will make them shrivel up in very hot weather, wedon`t know what to think now.