I had to have a rose and since being in France one of my favorites - 2 of which we inherited in our garden is Rosa "Madame Alfred Carriere" - it's one of the most prolific flowering rambling roses that I've come across that carries on flowering from early summer right up till late autumn. It has creamy/white blooms with hints of pink and smells absolutely gorgeous!
My next choice is the Oriental Poppy - these don't have such a long flowering period but are stunning and once the leaves have died back, new ones are formed which stay all winter until the new blooms arrive - having quite a good collection of these in my garden I really couldn't imagine a garden without them.... great for pollinating insects too!
My final choice is Camelia sasanqua "Evangelica" which is probably one of the latest additions to our garden - it flowers from late autumn and has only just stopped - it has the most amazing deep pink flowers with a mass of yellow stamens in the middle and gives a real splash of brightness in the garden at a time when very little else is out.
Shirley never mentioned we couldn't take seeds with us... might just pop in the odd sweet pea seed or maybe a few sunflower seeds too! ;-)