I'm want to buy a tree as a wedding gift for some firends

I think that it's a beautiful thought, too, James....Unfortunately, reality intrudes, as usual! I suspect that there is no tree that will grow indoors, bloom (at any time) and then grow outdoors in the UK. There's no chance that they actually live in the tropics, or a mild Mediterranean climate, do they?

I just had a thought, though. Some Camellias can be grown indoors in a cool, bright conservatory. Hard to reproduce those conditions in the average flat, though. Aarrgghh!

Sorry, wish that I was more help!

A Japanese Magnolia Tree fits all your requests. It will need a bright spot indoors then a sunny, sheltered spot outside. Being a Magnolia you also have flowering in spring with lovely white or pinkish flowers.

I'm finding that the term "Japanese Magnolia" is being used for many kinds of deciduous Magnolias, but none have tips for growing them indoors, and I was unaware that that was possible. Is there a specific species or hybrid that you are thinking of, Kildermorie?

We grew a Lennei, probably a Lennei Alba (can't confirm as tag is long gone and some flowers were more pinkish than pure white). It must have been around 2-3 years when we got it and it lived in a bay window (E-SE position). When it lost its most of its leaves in Oct-Nov it was put out in E facing balcony (sheltered). It still flowers in my dad's garden (SW part, but sheltered by fence and close to house).