It depends on just how large they are. If they are decent sized plants, then they will do best planted out in the garden. If still on the small side then the main objective will be to protect them from winter wet. I have devised a lot of covers that I attach to a fence with the plants sheltering beneath them. No sides and they are sitting on gravel. A cold frame or unheated greenhouse will do but don't shut them down tight, the plants need plenty of ventillation. They will need watering occaisionally but not too often and not too much - definitely not if a freezing spell is forcast.

Tough as old boots ..The penstemon can be a bit mard bung that one in the greenhouse.

The wallflower should really have been sown outside, so that you could plant them in their flowering position in october, if you have them inside, you will need to harden them off before you plant them out, but they can still be
planted in october for flowering next spring. derekm

thanks for your help everyone.