How big are the pots, both depth and width?

24in x 24in. Cheers

Let me just check your measurement - you're saying your pots are two feet from top to bottom (depth) and 24 inches across the top? Are they square, round, or much more narrow at the bottom (if you can't post a photo) and what are they made of? And you want something permanent, do you want something that looks good in winter too, or do you only care what they look like in summer? Are you close enough to the coast to get salt spray in the wind?

Pots are round, and slightly smaller towards bottom, prefer something permanent with colour in the summer , based near the coast but little chance of sea spray. Thanks

Correction, Preferably something that has a bit colour all year where in summer I can add some summer bedding for a bit more colour during the summer months.....Cheers

With pots that size, you could choose a shrub such as one of the smaller Camellias, or one of the many Pieris japonica varieties, or even Box topiary - for the first couple of years, you could probably get a bit of summer bedding in with them, but after that, the roots will take over the pot and you won't be able to. I think you have to decide whether you're prepared to just choose a small evergreen, like a dwarf conifer, for the central portion of the pot, and always replant round the edges each year, or whether you want to devote each one to a larger, permanent evergreen shrub. The drawback with choosing a dwarf plant for the centre surrounded by temporary flowering stuff for summer is the pot may look 'unbalanced' because its 2 feet deep with plants that are only a foot or so high in the top.