Will my salvias I have in small pots need protection during Winter, or is it OK to leave them out in the open. Should I cut them back... I've added a photo of the pots they are in. Many thanks.
What kind are they, do you know?
I would leave the growth on and cut back in Spring when the possibility of frost is over. Mulch around the base of the plants with a top dressing of compost, or shredded fern leaves to add extra protection.
Also, lift your pot off the ground by a couple of inches (stand it on bricks or similar) as that will allow excess moisture to drain out. Wrapping your pot in bubble wrap will protect it from becoming cracked/damaged in harsh cold temperatures.
In Spring, cut old growth back when you see new young growth, but still be aware of late frosts and cover with horticultural fleece if they are forecast.
A gardener's work is never at an end - (John Evelyn 1620-1706)
...Yes, they are Salvia nemorosa Sensation compact Blue.
Salvia nemorosa should be fully hardy, and yes you can cut it back to the base when the stems die off naturally. Depending on where you are (cold vs mild winters) the frost-proofing of pots may be advisable as yorkshirerose says.
The thing you may find is that, because the pots are small, the Salvias outgrow them next season. Options are to plant out in the open border, or divide, remove the old soil and replace with fresh compostand water-retentive gel, and plant a vigorous looking division in each pot. Give them timed release fertiliser in the spring and away you should go.