You don't say if the spot is shady or sunny. How about Nandina domestica for attractive leaves, flowers and autumn colour. Be aware that 'all year interest' can mean 'boring'!! Sometimes it's nice to see the leaves change and fall leaving a twiggy outline all winter. Then the excitement of buds bursting. If the spot is sheltered and sunny, try Trachecarpus fortunei, a hardy palm. You could also tuck some crocuses etc around the edge of the pot for spring colour.

Couple of questions for you, Suehopkins - is the area hot and sunny, or is it shady, or half and half? (I'd prefer to ask if its north or south facing, but people don't always know, lol!)
And secondly, do you need to walk past it either side? If you do, you'd need a particular growth habit so you were still able to after a couple of years...

...without getting soaked! Good thinking Bamboo!