Suggestions please for suitable shrubs/ small trees for large containers

A couple of blueberries could be good. If you get two different varieties they crop better.

I have a Prunus Incisa 'Kojo-No-Mai Fuji cherry which is an absolute delight. It is covered with small white flowers in Spring, then turns a lovely green in Summer, Autumn sees lovely shades of red and in Winter the slightly twisted shape of the branches is displayed which gives structure and interest during the colder months. Mine is in a large pot but when bought was very small and I have watched and enjoyed it grow over several years and all the seasons.

Oleander is lovely, but don’t get it if you have a dog - they are poisonous for dogs. An olive tree is beautiful, but they are expensive. Both like sun. Rosemary is another good one, and bay - herb shrubs are both functional and attractive.

Acer Palmatum, Orange Dream. It's the most stunning colour in late summer, early autumn, just when your herbaceous borders are starting to look a bit bare.

I have 6 blueberries in 6 pots that size. They are incredibly productive and are lovely shrubs in their own right, they will be turning red soon. This year they gave me 7kg of organic blueberries, now in the freezer. They don`t get pests. They need tlc as in enough watering through summer with rain. Right now they are around 6 foot tall and at their maximum I think

Last house I had lilacs in large pots, they were also good. Acer palmatum too, it is a very beautiful plant, needs to be out of the wind, mine was red and in the same pot for a very long time

I have a large spare pot, I am tempted by that prunus toscalily, what conditions does it like?

I am in the NW about 200ft above sea level so can be a bit rainy, have just potted it on and given an Autumn/Spring feed. Like anything in a pot you need to watch that it does not suffer too much in draught but that's not usually a problem here. Seems very forgiving whereas Chewbacca suggested an Acer and I have made several attempts at growing them and never succeed which is a pity as I like them a lot.

Thank you toscalily

Have you thought of Christmas Box, they flower December/February just when life is somewhat drear and the smell is amazing!

Great suggestions so far thank you.

I have a Japanese cedar in one of my pots. I think it is a very elegant tree and you can prune it to keep it the size you want.

I do not have a greenhouse so choose plants that will survive a hard frosts and winds in the winter in a pot. 'Zigibar mirga' (hardy -21c ginger) flowers on the soil below the leaves. Stems edible. Toss a packet of viola/pansy seeds around plants in a pot and you have all year colour. They reseed year after year.
Everlasting sweet peas for colour from May to Dec. add a lily bulb for scent also deters slugs. A trellis climber frame at the back of the pot for a stunning display or let them run onto garden or path.
My all time favorite are hosta.
Geranium 'chelsee' flower June - Nov. an amazing blue flower.

If you cut the base off a plastic water bottle, insert it upside down near the roots as you plant any tub you can fill bottle with water when empty. This saves water and your plants never get over or under watered.