If they are in the ground I would have thought they will be fine, if in pots you could protect the roots with some sort of insulation. They will have lost their leaves by now.

I agree with Maggy they should be fine if in the ground. I planted a small weeping cherry 2 years ago and it is doing well. It had no problems coming through Hungarian winters which are colder than UK, so hope your trees do well.

As the others are implying, you don't need to if they're in the ground.

Cherry trees will be fine, they are very hardy. Mine have been in the ground for 6 years and no problems. You mentioned other fruit trees, what are those?

Within reasonable limits--i.e., short of the Arctic Circle--winter frost is good for deciduous fruit trees. Not so much late frosts that nip the new growth and flowers! Hence the poem, "Goodbye, and Keep Cold", by Robert Frost.

the only protection they could need is if you have pests as rabbits etc love new saplings .