Camellia
Most Camellias that you will come accross in a garden centre will be Camellia japonica types. They are hardy and have a huge variety of colours and forms, flowering generally from February to early May. Well worth having for early flowers. However they will not tolerate alkalin soils and very quickly become chlorotic.
This is a single flowering red
… and this a double flowering White.
There are hundreds of different species and varieties to choose from.