can anyone advise me i have just went down to my greenhouse and my pots are frozen i am growing sweet peas pansies violas will the plants be okay or would it be better to get a heater .
Those plants are all OK, hardy. My pansies and violas are planted outside all winter, Sweet Peas in unheated, but covered, cold frame.
Wills, they're all hardy - they'll be fine.
A heater will only cause condensation which will provide the perfect breeding ground for moulds and botrytis etc and they will kill your plants!
Let your sweet peas defrost slowly out of direct sunlight, which will burst the cells in their leaves. You will soon see whether they have been really damaged as the plants will look as if they have been blow torched in a few days time,
Pansies and violas, however, which are the same genus, will survive at least minus 18-,mine have in past years with no protection at all in exposed ground - most have mountain viola genes bred into them .