I wouldn't, personally.

not really necessary as the amount of growth they put on in the winter is minimal. come spring I'd be tempted but then only weakly and monthly.
if the winter stays mild then I might be tempted to give them a light feed. but dead head regularly will do more to keep them in flower than anything else.

Thankyou Badfish and SBG. They aren't flowering yet so I think I'll give them a weak feed and then leave until spring.

Every year I have bought packs of the small flowered violas and grown them in two hanging baskets at the back of the house. This year, don't know why, I have not done so. If they are planted in fresh compost the goodness in that should see them into spring. Then I would lightly feed them, say every two weeks, and dead head them. You will find that around May or June they start to go off....this is the time I cut them right down, taking all the growth off, and within 2 weeks or so you will find good fresh growth and a resurgance of flowers for the summer weeks.
Hope this helps.

Yes it helps a lot John so thankyou for the growing tips.