First, this poor plant is far too big for the pot its in - please either plant out in the garden, or give it a much larger pot, making sure you tease the roots out from the inevitable, tight packed coil I suspect you'll find inside. Second, shear it over a bit after the flowers are done, or when you repot. As for feeding, Miracle Gro general purpose - tomato food not an appropriate feed for a foliage plant like this.

Thank you Bamboo very much, that is great advice. Will to exactly as you suggest. Will have to wait until my son comes down as I could never do this myself. The whole thing weighs more than I do.