Posted: 21/07/2014 at 09:34
I think I'd go for a potted selection of Canna Lillies. You'll have plenty of good suppliers in London, and I'm sure a local Garden centre will be able to help. It would fit what you require as well, colour, spikes and they look very good in pots. They are frost tender, but in London winter temperatures never get far below freezing, so they could probably stay outside all year. I'll let someone else suggest a shrub.