You will need to keep pots well watered, as plants act like an umbrella over pots, so they normally need to be watered daily.

Euonymus, especially the japonicus Ovatus Aureus springs to mind immediately for seaside pots with partial sun, though they are a tad boring.

Phormiums do well at seaside locations - and look good in pots. Phormium 'bronze baby' is quite stunning all year round. That will tolerate am sun only.

A website called gardeningdata.co.uk has a very long list of plants for seaside locations.

tamarisk is an excellent seaside shrub

Thank you to Kildermorie, Inverglen and Bernadetteh for their helpful advice re. suitable plant.

PeeCee