You don't say whether you just want temporary planting, or something permanent like a small shrub (it will have to be small, the pot isn't big enough for anything over a foot or so).

heathers/ericas.

thanks girls i hopely intend to have plants for summer then remove them and put in some autumn/winter

In shade, one busy lizzy and trailing lobelia will fill the pot, though it will do well in sun too if watered frequently.

thanks to all who replied------------- have opted for a dark red minature rose