Beautiful Pot Plant

Hydrangeas flower for a long time. Use a big pot - they can get quite large.
Sorry - doesn't keep green leaves all year. (I should read the question properly!)

A camellia may fit the bill. They have red or white or pink or occasionally yellow flowers and ours used to be in flower from just before Christmas to the end of May. That's an established plant, sheltered from the wind by a wall, and in Cornwall. The variety we used to have was 'Diamond Head' but there are literally hundreds, if not thousands, to chose from.

Realistically though Beattie camellias prefer to be in the ground rather than in a container...

Another thought - what about a Hebe? They flower for a long time and come in purple/ lilac/ pink/ white shades.

I agree with you, MG, but that goes for almost all plants, especially shrubs and trees, yet lots are grown in pots, containers and tubs.

So long as the owner is prepared to properly look after!

Hebe is easier to look after and will do well in full sun. Camelias prefer partial shade and need ericaceous compost. It depends where you are going to site it.

But come to think of it, if there was such a plant surely everybody would have one? Probably some compromise is needed